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GATE SOLVED PAPER 
Electronics & Communication 
Engineering Mathematics 
Copyright © By NODIA & COMPANY 
Information contained in this book has been obtained by authors, from sources believes to be reliable. However, 
neither Nodia nor its authors guarantee the accuracy or completeness of any information herein, and Nodia nor its 
authors shall be responsible for any error, omissions, or damages arising out of use of this information. This book 
is published with the understanding that Nodia and its authors are supplying information but are not attempting 
to render engineering or other professional services. 
NODIA AND COMPANY 
B-8, Dhanshree Tower Ist, Central Spine, Vidyadhar Nagar, Jaipur 302039 
Ph : +91 - 141 - 2101150 
www.nodia.co.in 
email : enquiry@nodia.co.in
GATE SOLVED PAPER - EC 
ENGINEERING MATHEMATICS 
2013 ONE MARK 
Q. 1 The maximum value of q until which the approximation sinq . q holds to within 
10% error is 
(A) 10c (B) 18c 
(C) 50c (D) 90c 
Q. 2 The minimum eigen value of the following matrix is 
R 
3 
5 
2 
5 
12 
7 
2 
7 
5 
SSSS 
WWWW 
© www.nodia.co.in 
T 
V 
X 
(A) 0 (B) 1 
(C) 2 (D) 3 
4 
Q. 3 A polynomial f (x) a4x a 3 
x a x a x a 
3 
2 
2 
= + + + 1 - 0 with all coefficients positive has 
(A) no real roots 
(B) no negative real root 
(C) odd number of real roots 
(D) at least one positive and one negative real root 
2013 TWO MARKS 
Q. 4 Let A be an m#n matrix and B an n#m matrix. It is given that determinant 
^Im + ABh = determinant ^In + BAh, where Ik is the k#k identity matrix. Using 
the above property, the determinant of the matrix given below is 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
R 
SSSSS 
S 
T 
V 
WWWWW 
W 
X 
(A) 2 (B) 5 
(C) 8 (D) 16 
2012 ONE MARK 
Q. 5 With initial condition x(1) = 0.5, the solution of the differential equation 
t dx dt 
+ x = t , is 
(A) x t 2 
= - 1 (B) x = t 2- 1 
2 
= (D) x t2 
(C) x t 
2 
2 
=
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
= 1 
2 + - + . 
Q. 6 Given f (z) z 1 z 
3 
If C is a counter clockwise path in the z -plane such that z + 1 = 1, the value of 
1 
2 j f (z)dz 
C p # is 
(A) -2 (B) -1 
(C) 1 (D) 2 
Q. 7 If x = -1, then the value of xx is 
(A) e-p/2 (B) ep/2 
(C) x (D) 1 
2012 TWO MARKS 
© www.nodia.co.in 
Q. 8 Consider the differential equation 
d y t 
dy t 
2 y t 2 
( ) ( ) 
( ) 
dt 
dt 
2 
dy 
+ + = d(t) with y(t) =- 2 and dt = 
0 
t 
t 
0 
0 
= 
= 
- 
- 
dy 
The numerical value of dt 
t=0+ 
is 
(A) -2 (B) -1 
(C) 0 (D) 1 
Q. 9 The direction of vector A is radially outward from the origin, with A = krn . 
where r2 = x2+ y2+ z2 and k is a constant. The value of n for which d:A = 0 is 
(A) -2 (B) 2 
(C) 1 (D) 0 
Q. 10 A fair coin is tossed till a head appears for the first time. The probability that the 
number of required tosses is odd, is 
(A) 1/3 (B) 1/2 
(C) 2/3 (D) 3/4 
Q. 11 The maximum value of f (x) = x3- 9x2+ 24x + 5 in the interval [1,6] is 
(A) 21 (B) 25 
(C) 41 (D) 46 
Q. 12 Given that 
- - 
> H = > H, the value of A3 is 
5 
2 
3 
0 
A and I 
1 
0 
0 
= 1 
(A) 15A+ 12I (B) 19A+ 30I 
(C) 17A+ 15I (D) 17A+ 21I 
2011 ONE MARK 
Q. 13 Consider a closed surface S surrounding volume V . If rv is the position vector of a 
## v $ t 
point inside S , with nt the unit normal on S , the value of the integral 5r n dS 
S 
is 
(A) 3V (B) 5V 
(C) 10V (D) 15V
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
dy = ky y = c is 
Q. 14 The solution of the differential equation dx , (0) 
(A) x = ce-ky (B) x = kecy 
(C) y = cekx (D) y = ce-kx 
Q. 15 The value of the integral 
# - + where c is the circle z = 1 is given 
z dz 
4 5 
3 4 
2+ + 
(z z ) 
by 
c 
(A) 0 (B) 1/10 
(C) 4/5 (D) 1 
2011 TWO MARKS 
Q. 16 A numerical solution of the equation f (x) + x - 3 = 0 can be obtained using 
Newton- Raphson method. If the starting value is x = 2 for the iteration, the 
value of x that is to be used in the next step is 
(A) 0.306 (B) 0.739 
(C) 1.694 (D) 2.306 
© www.nodia.co.in 
Q. 17 The system of equations 
+ + = 
+ + = 
+ + = 
x y z 
x y y 
x y z 
6 
4 6 20 
4 
l m 
has NO solution for values of l and μ given by 
(A) l = 6, m = 20 (B) l = 6, m =Y 20 
(C) l =Y 6, m = 20 (D) l =Y 6, m = 20 
Q. 18 A fair dice is tossed two times. The probability that the second toss results in a 
value that is higher than the first toss is 
(A) 2/36 (B) 2/6 
(C) 5/12 (D) 1/2 
2010 ONE MARKS 
Q. 19 The eigen values of a skew-symmetric matrix are 
(A) always zero (B) always pure imaginary 
(C) either zero or pure imaginary (D) always real 
Q. 20 The trigonometric Fourier series for the waveform f (t) shown below contains 
(A) only cosine terms and zero values for the dc components
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
(B) only cosine terms and a positive value for the dc components 
(C) only cosine terms and a negative value for the dc components 
(D) only sine terms and a negative value for the dc components 
Q. 21 A function n(x) satisfied the differential equation 
2 
d n x 
n x 
( ) ( ) 
dx 
2 - = 
0 2 
L 
where L is a constant. The boundary conditions are :n(0) = K and n(3) = 0. 
The solution to this equation is 
(A) n(x) = Kexp(x/L) (B) n(x) = Kexp(- x/ L) 
(C) n(x) = K2exp(- x/L) (D) n(x) = Kexp(- x/L) 
2010 TWO MARKS 
© www.nodia.co.in 
Q. 22 If ey = x1/x , then y has a 
(A) maximum at x = e (B) minimum at x = e 
(C) maximum at x = e-1 (D) minimum at x = e-1 
Q. 23 A fair coin is tossed independently four times. The probability of the event “the 
number of time heads shown up is more than the number of times tail shown up” 
(A) 1/16 (B) 1/3 
(C) 1/4 (D) 5/16 
v = t + 2 t , then A dl 
Q. 24 If A xyax x ay 
# v $ v over the path shown in the figure is 
C 
(A) 0 (B) 
2 
3 
(C) 1 (D) 2 3 
Q. 25 The residues of a complex function 
( ) 
- 
( )( ) 
x z 
z z z z 
1 2 
= 1 2 - - 
at its poles are 
(A) 1 
2, 
- 1 2 
and 1 (B) 1 
2 
, - 1 and -1 
2 
1 and 2 
(C) 2, 1 
-3 (D) , 2 
1 - 1 and 2 
3 
Q. 26 Consider differential equation 
dy x 
( ) 
dx ( ) 
- y x = x , with the initial 
condition y(0) = 0. Using Euler’s first order method with a step size of 0.1, the 
value of y(0.3) is 
(A) 0.01 (B) 0.031 
(C) 0.0631 (D) 0.1
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Q. 27 Given ( ) 
- 1 3 s 
+ 1 
; E. If limf (t) 1 
3 2 = 
+ + - 
s 4 s k 3 
s 
( ) 
f t L 
t 
= 
"3 
, then the value 
of k is 
(A) 1 (B) 2 
(C) 3 (D) 4 
2009 ONE MARK 
Q. 28 The order of the differential equation 
2 3 
+ + 4 = - c m is 
d y 
dt 
dy y et 
dt 
2 
(A) 1 (B) 2 
(C) 3 (D) 4 
Q. 29 A fair coin is tossed 10 times. What is the probability that only the first two 
tosses will yield heads? 
(A) 2 
10 1 
c 1 m 2 (B) C 2 
2 
2 b l 
1 10 c m (D) C 2 
(C) 2 
10 1 
2 
co.in 
nodia.www.© 10 b l 
= + -1, then 
Q. 30 If f (z) c0 c1z 
# + f z 
is given by 
( ) 
z 
dz 
1 
unit circle 
(A) 2pc1 (B) 2p(1 + c0) 
(C) 2pjc1 (D) 2p(1 + c0) 
2009 TWO MARKS 
Q. 31 The Taylor series expansion of sin 
x 
x 
- p at x = p is given by 
(A) 
+ ( - p ) 
2 + (B) 
! 
... 
x 
1 
3 
- - ( - p ) 
2 + 
! 
... 
x 
1 
3 
(C) 
- ( - p ) 
2 + (D) 
! 
... 
x 
1 
3 
- + ( - p ) 
2 + 
! 
... 
x 
1 
3 
Q. 32 Match each differential equation in Group I to its family of solution curves from 
Group II 
Group I Group II 
A. 
dy 
dx 
= y 1. Circles 
x 
B. 
dy 
dx 
=-y 2. Straight lines 
x 
C. 
dy 
dx 
y x 
= 3. Hyperbolas 
D. 
dy 
dx 
y x 
=- 
(A) A - 2, B - 3,C - 3,D - 1 
(B) A - 1, B - 3,C - 2,D - 1 
(C) A - 2, B - 1,C - 3,D - 3 
(D) A - 3, B - 2,C - 1,D - 2
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Q. 33 The Eigen values of following matrix are 
R 
- 
- - 
1 
3 
0 
3 
1 
0 
5 
6 
3 
SSSS 
T 
V 
WWWW 
X 
(A) 3, 3 + 5j, 6 - j (B) -6 + 5j, 3 + j, 3 - j 
(C) 3 + j, 3 - j, 5 + j (D) 3, - 1 + 3j, - 1 - 3j 
2008 ONE MARKS 
Q. 34 All the four entries of the 2 # 2 matrix P 
p 
p 
p 
p 
11 
21 
12 
22 
= = G are nonzero, 
and one of its eigenvalue is zero. Which of the following statements is true? 
(A) p11p12- p12p21 = 1 (B) p11p22- p12p21 =- 1 
(C) p11p22- p12p21 = 0 (D) p11p22+ p12p21 = 0 
© www.nodia.co.in 
Q. 35 The system of linear equations 
4x + 2y = 7 2x + y = 6 has 
(A) a unique solution 
(B) no solution 
(C) an infinite number of solutions 
(D) exactly two distinct solutions 
Q. 36 The equation sin(z) = 10 has 
(A) no real or complex solution 
(B) exactly two distinct complex solutions 
(C) a unique solution 
(D) an infinite number of complex solutions 
Q. 37 For real values of x , the minimum value of the function 
f (x) = exp(x) + exp(- x) is 
(A) 2 (B) 1 
(C) 0.5 (D) 0 
Q. 38 Which of the following functions would have only odd powers of x in its Taylor 
series expansion about the point x = 0 ? 
(A) sin(x3) (B) sin(x2) 
(C) cos (x3) (D) cos (x2) 
Q. 39 Which of the following is a solution to the differential equation 
dx t 
( ) 
( ) 
dt 
+ 3x t = 0 ? 
(A) x(t) = 3e-t (B) x(t) = 2e-3t 
(C) x(t) =- 3 t 2 (D) x(t) = 3t2 
2 
2008 TWO MARKS 
Q. 40 The recursion relation to solve x = e-x using Newton - Raphson method is 
= n + 
(A) xn e 
x 
1 
- (B) x x e n n 
x 
= - n + 
1 
- 
- 
x 
= + 
e 
n n n 1 x 
(C) x (1 x ) 
+ + - 
1 n 
e 
(D) 
- - - 
x e ( 1 x ) 
1 
x 
+ - 
x e 
n 
n 
x 
n 
x 
n 
1 
2 
n 
n 
= 
- 
-
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Q. 41 The residue of the function f (z) 
1 
2 2 = 
+ - 
(z 2) (z 2) 
at z = 2 is 
(A) 
- 1 (B) 
32 
- 1 
16 
(C) 
1 (D) 
16 
1 
32 
Q. 42 Consider the matrix P 
0 
2 
1 
= =- -3G. The value of ep is 
(A) 
- - 
- - 
2 1 
2 1 
- 
- 
e e 
e e 
- - 
1 2 
2 1 
- 
- 
e e 
e e 
2 3 
2 2 5 
> - - H 
(B) 
- - 
- 
1 1 
1 2 
+ 
- 
e e 
e e 
- - 
2 1 
1 2 
- 
+ 
e e 
2 
3 2 
> - - H 
2 4 e e 
(C) 
- - 
- - 
2 1 
2 1 
- 
- 
e e 
e e 
- - 
1 2 
2 1 
- 
+ 
e e 
e 
5 
2 6 
3 
4 6 
> - - H 
(D) 
- - 
- - 
1 - 
2 
1 2 
e e 
e e 
- - 
1 - 
2 
1 2 
e e 
e e 
2 
2 2 2 
> - - H 
- + 
- + 
© www.nodia.co.in 
Q. 43 In the Taylor series expansion of exp(x) + sin(x) about the point x = p, the 
coefficient of (x - p)2 is 
(A) exp(p) (B) 0.5 exp(p) 
(C) exp(p) + 1 (D) exp(p) - 1 
Q. 44 The value of the integral of the function g(x,y) = 4x3+ 10y4 along the straight 
line segment from the point (0,0) to the point (1,2) in the x - y plane is 
(A) 33 
(B) 35 
(C) 40 
(D) 56 
Q. 45 Consider points P and Q in the x - y plane, with P = (1,0) and Q = (0,1). The 
Q 
# + along the semicircle with the line segment PQ as 
line integral 2 (xdx ydy) 
P 
its diameter 
(A) is -1 
(B) is 0 
(C) is 1 
(D) depends on the direction (clockwise or anit-clockwise) of the semicircle 
2007 ONE MARK 
Q. 46 The following plot shows a function which varies linearly with x . The value of the 
integral I ydx 
1 
2 
= # is
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
(A) 1.0 (B) 2.5 
(C) 4.0 (D) 5.0 
Q. 47 For x << 1, coth (x) can be approximated as 
(A) x (B) x2 
(C) 
1 (D) 
x 
1 
2 
x 
q 
b l is 
sin 2 
0 q 
Q. 48 lim 
q" 
(A) 0.5 (B) 1 
(C) 2 (D) not defined 
Q. 49 Which one of following functions is strictly bounded? 
(A) 1/x2 (B) ex 
in 
(C) x2 co.(D) e - x2 
nodia.www.© Q. 50 For the function e-x , the linear approximation around x = 2 is 
(A) (3 - x)e-2 
(B) 1 - x 
(C) 63 + 3 2 - (1 - 2)x @e-2 
(D) e-2 
2007 TWO MARKS 
Q. 51 The solution of the differential equation k 
2 d y y y 
dx 
2 
2 
= - 2 under the boundary 
conditions 
(i) y = y1 at x = 0 and 
(ii) y = y2 at x = 3, where k,y1 and y2 are constants, is 
x y = 1- 2 a- 2 k+ 2 
(A) y (y y )exp 
k 
x y = 2- 1 a- k+ 1 
(B) y (y y )exp k 
x y = ^ 1- 2h a k+ 1 
(C) y y y sinh k 
x y = ^ 1- 2h a- k+ 2 
(D) y y y exp k 
Q. 52 The equation x3- x2+ 4x - 4 = 0 is to be solved using the Newton - Raphson 
method. If x = 2 is taken as the initial approximation of the solution, then next 
approximation using this method will be 
(A) 2/3 (B) 4/3 
(C) 1 (D) 3/2 
Q. 53 Three functions f1(t), f2(t) and f3(t) which are zero outside the interval [0, T] are 
shown in the figure. Which of the following statements is correct?
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
© www.nodia.co.in 
(A) f1(t) and f2(t) are orthogonal (B) f1(t) and f3(t) are orthogonal 
(C) f2(t) and f3(t) are orthogonal D) f1(t) and f2(t) are orthonormal 
Q. 54 If the semi-circular control D of radius 2 is as shown in the figure, then the value 
of the integral 
# 1 
ds 
is 
(s 2 - 1 
) 
D 
(A) jp (B) -jp 
(C) -p (D) p 
Q. 55 It is given that , ... X X XM 
1 2 at M non-zero, orthogonal vectors. The dimension of 
the vector space spanned by the 2M vectors X1,X2,...XM, - X1, - X2,... - XM is 
(A) 2M (B) M+ 1 
(C) M 
(D) dependent on the choice of , ,... X X XM 
1 2 
Q. 56 Consider the function f (x) = x2- x - 2. The maximum value of f (x) in the closed 
interval [- 4, 4] is 
(A) 18 (B) 10 
(C) -225 (D) indeterminate 
Q. 57 An examination consists of two papers, Paper 1 and Paper 2. The probability 
of failing in Paper 1 is 0.3 and that in Paper 2 is 0.2. Given that a student has 
failed in Paper 2, the probability of failing in Paper 1 is 0.6. The probability of a 
student failing in both the papers is 
(A) 0.5 (B) 0.18 
(C) 0.12 (D) 0.06
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
2006 ONE MARK 
Q. 58 The rank of the matrix 
R 
1 
1 
1 
1 
1 
1 
1 
0 
1 
- 
SSSS 
T 
V 
WWWW 
X 
is 
(A) 0 (B) 1 
(C) 2 (D) 3 
Q. 59 4#4# P, where P is a vector, is equal to 
(A) P P 2P #4# -4 (B) 42P +4 (4# P) 
(C) 42P +4# P (D) 4(4$ P) -42P 
Q. 60 ## (4# P) $ ds , where P is a vector, is equal to 
(A) # P $ dl (B) # 4#4# P $ dl 
(C) # 4# P $ dl (D) ### 4$ Pdv 
© www.nodia.co.in 
Q. 61 A probability density function is of the form p(x) = Ke-a x ,x ! (-3,3). The 
value of K is 
(A) 0.5 (B) 1 
(C) 0.5a (D) a 
Q. 62 A solution for the differential equation xo (t) + 2x(t) = d(t) with initial condition 
x(0-) = 0 is 
(A) e-2tu(t) (B) e2tu(t) 
(C) e-tu(t) (D) etu(t) 
2006 TWO MARKS 
Q. 63 The eigenvalue and the corresponding eigenvector of 2 # 2 matrix are given by 
Eigenvalue Eigenvector 
l1 = 8 v 
1 
1 
1 == G 
l2 = 4 v 
1 
1 
2 = 
= G 
- 
The matrix is 
(A) 
6 
2 
2 
= 6G (B) 
4 
6 
6 
= 4G 
(C) 
2 
4 
4 
= 2G (D) 
4 
8 
8 
= 4G 
Q. 64 For the function of a complex variable W = lnZ (where, W = u + jv and Z = x + jy 
, the u = constant lines get mapped in Z -plane as 
(A) set of radial straight lines (B) set of concentric circles 
(C) set of confocal hyperbolas (D) set of confocal ellipses 
Q. 65 The value of the constant integral 
1 
# dz is positive sense is 
z 4 
z j 
2 
2 
+ 
- = 
(A) j 
p (B) 
2 
2 p 
- 
- p (D) 
(C) j 
2 
2 p
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
q q p # is given by 
Q. 66 The integral sin3 d 
0 
(A) 
1 (B) 
2 
2 
3 
(C) 
3 4 
(D) 
8 
3 
Q. 67 Three companies X,Y and Z supply computers to a university. The percentage 
of computers supplied by them and the probability of those being defective are 
tabulated below 
Company % of Computer Supplied Probability of being supplied defective 
X 60% 0.01 
Y 30% 0.02 
Z 10% 0.03 
Given that a computer is defective, the probability that was supplied by Y is 
(A) 0.1 (B) 0.2 
(C) 0.3 (D) 0.4 
© www.nodia.co.in 
Q. 68 For the matrix 
4 
2 
2 
= 4G the eigenvalue corresponding to the eigenvector 
101 
=101G is 
(A) 2 
(B) 4 
(C) 6 
(D) 8 
Q. 69 For the differential equation 
2 
d y k y 0 2 
dx 
+ 2 = the boundary conditions are 
(i) y = 0 for x = 0 and (ii) y = 0 for x = a 
The form of non-zero solutions of y (where m varies over all integers) are 
(A) y A sin 
=/ m p x 
(B) y A cos 
a 
m 
m 
=/ p 
m x 
a 
m 
m 
= / m 
p (D) y Ame a 
(C) y Amx a 
m 
= / - p 
m x 
m 
Q. 70 As x increased from -3 to 3, the function f (x) 
e 
1 e 
x 
x 
= 
+ 
(A) monotonically increases 
(B) monotonically decreases 
(C) increases to a maximum value and then decreases 
(D) decreases to a minimum value and then increases 
2005 ONE MARK 
Q. 71 The following differential equation has 
2 3 2 c m+ c m + + = x 
3 d y 
4 dy y 2 2 
dt 
dt 
(A) degree = 2, order = 1 (B) degree = 1, order = 2 
(C) degree = 4, order = 3 (D) degree = 2, order = 3
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Q. 72 A fair dice is rolled twice. The probability that an odd number will follow an even 
number is 
(A) 1/2 (B) 1/6 
(C) 1/3 (D) 1/4 
Q. 73 A solution of the following differential equation is given by 
© www.nodia.co.in 
d y 
dx 
5 dy 6y 0 2 
dx 
2 
- + = 
(A) y = e2x + e-3x (B) y = e2x + e3x 
(C) y = e-2x + 33x (D) y = e-2x + e-3x 
2005 TWO MARKS 
Q. 74 In what range should Re(s) remain so that the Laplace transform of the function 
e(a+2)t+5 exits. 
(A) Re(s) > a + 2 (B) Re(s) > a + 7 
(C) Re(s) < 2 (D) Re(s) > a + 5 
Q. 75 The derivative of the symmetric function drawn in given figure will look like 
Q. 76 Match the following and choose the correct combination: 
Group I Group 2 
E. Newton-Raphson method 1. Solving nonlinear equations 
F. Runge-kutta method 2. Solving linear simultaneous 
equations 
G. Simpson’s Rule 3. Solving ordinary differential 
equations 
H. Gauss elimination 4. Numerical integration 
5. Interpolation 
6. Calculation of Eigenvalues 
(A) E - 6, F - 1,G - 5, H - 3 (B) E - 1, F - 6,G - 4, H - 3 
(C) E - 1, F - 3,G - 4, H - 2 (D) E - 5, F - 3,G - 4, H - 1 
Q. 77 Given the matrix 
- 
= G, the eigenvector is 
4 
4 
2 
3 
(A) 
3 
=2G (B) 
4 
=3G 
(C) 
2 
=-1G (D) 
- 
= G 
1 
2
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Q. 78 Let, 
0 1 
. 
A 
2 
0 
- 
= G and A 
= 3 
1 2 1 
a 
0 b 
- = = G. Then (a + b) = 
(A) 7/20 (B) 3/20 
(C) 19/60 (D) 11/20 
2 
# c m is 
Q. 79 The value of the integral I = 1 
3 
exp - x dx 
2 
8 
p 0 
(A) 1 (B) p 
(C) 2 (D) 2p 
Q. 80 Given an orthogonal matrix 
A 
R 
1 
1 
1 
0 
1 
1 
1 
0 
1 
1 
0 
1 
1 
1 
0 
1 
SSSSS 
= - 
- - 
T 
V 
WWWWW 
X 
6AAT @-1 is 
1 
SSSSSS 
WWWWWW 
SSSSSS 
WWWWWW 
0 
(A) 
0 
in 
0 
co.nodia.www.© 0 
1 
0 
0 
0 
0 
0 
0 
0 
0 
4 
4 
2 1 
2 1 
R 
T 
V 
X 
(B) 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
0 
2 1 
2 1 
2 1 
2 1 
R 
T 
V 
X 
(C) 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
R 
SSSSS 
T 
V 
WWWWW 
X 
(D) 
1 
SSSSSS 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
4 
4 
4 
1 
4 
R 
T 
V 
WWWWWW 
X 
***********
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
SOLUTIONS 
Sol. 1 Option (B) is correct. 
Here, as we know 
Limsin 
0 
q 
q" 
. 0 
but for 10% error, we can check option (B) first, 
= = p = 
q 18 18 . 
c c# 0 314 
180 
c 
sinq = sin18c = 0.309 
% error = 0 . 314 - 0 . 309 0 . 
309 
#100 % = 0 . 49 
% Now, we check it for q = 50c 
in 
q = 50 c = 50 c# p = 
0 . 
873 
180 
co.c 
sinq nodia.= sin50c = 0.77 
% error = 0.77 - 0.873 0 . 
873 =- 
12 . 25 % www.© so, the error is more than 10%. Hence, for error less than 10%, q = 18c can have 
the approximation 
sin q . q 
Sol. 2 Option (A) is correct. 
For, a given matrix A 6 @ the eigen value is calculated as 
A - lI = 0 
where l gives the eigen values of matrix. Here, the minimum eigen value among 
the given options is 
l = 0 
We check the characteristic equation of matrix for this eigen value 
A - lI = A (for l = 0) 
3 
5 
2 
5 
12 
7 
2 
7 
5 
= 
= 3^60 - 49h- 5^25 - 14h+ 2^35 - 24h 
= 33 - 55 + 22 
= 0 
Hence, it satisfied the characteristic equation and so, the minimum eigen value 
is 
l = 0 
Sol. 3 Option (D) is correct. 
Given, the polynomial 
f^xh a4x 4 
a x 3 
a x 2 
3 
2 
a x a 
= + + + 1 - 0 
Since, all the coefficients are positive so, the roots of equation is given by 
f^xh = 0 
It will have at least one pole in right hand plane as there will be least one sign 
change from ^a1h to ^a0h in the Routh matrix 1st column. Also, there will be a
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
corresponding pole in left hand plane 
i.e.; at least one positive root (in R.H.P) 
and at least one negative root (in L.H.P) 
Rest of the roots will be either on imaginary axis or in L.H.P 
Sol. 4 Option (B) is correct. 
Consider the given matrix be 
Im + AB 
R 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
1 
V 
1 
1 
1 
2 
= 
SSSSS 
S 
T 
WWWWW 
W 
X 
where m = 4 so, we obtain 
AB 
R 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
1 
V 
1 
1 
1 
2 
R 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
0 
V 
0 
0 
0 
1 
SSSSS 
WWWWW 
= - 
S 
T 
SSSSS 
S 
T 
W 
X 
WWWWW 
W 
X 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
1 
SSSSS 
WWWWW 
= 
co.in 
nodia.www.© R 
S 
T 
V 
W 
X 
1 
1 
1 
1 
= 
R 
SSSSS 
S 
T 
V 
WWWWW 
W 
X 
61 1 1 1@ 
Hence, we get 
A 
1 
1 
1 
1 
= 
R 
SSSSS 
S 
T 
V 
WWWWW 
W 
X 
, B = 81 1 1 1B 
R 
Therefore, BA = 81 1 1 1B 1 
SSSSS 
WWWWW 
1 
1 
1 
S 
T 
V 
W 
X 
= 4 
From the given property 
Det ^Im + ABh = Det^Im + BAh 
& Det 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
1 
1 
1 
1 
2 
R 
SSSSS 
S 
T 
V 
WWWWW 
W 
X 
Det 
R 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
0 
0 
0 
0 
1 
SSSSS 
WWWWW 
]] 
]] 
= + 4 
S 
T 
V 
W 
X 
Z 
[ 
 
_ 
bb 
bb 
` 
a 
= 1 + 4 
= 5 
Note : Determinant of identity matrix is always 1. 
Sol. 5 Option (D) is correct. 
dx + x = t 
t dt
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
dx 
dt 
t x 
+ = 1 
dx + Px = Q (General form) 
dt 
1dt = # = # = = 
Integrating factor, IF e Pdt e t elnt t 
Solution has the form, 
x#IF = # ^Q#IFhdt + C 
x#t = # (1) (t)dt + C 
2 
xt = t2 + 
C 
Taking the initial condition, 
x(1) = 0.5 
t2 
0.5 = 1 2 co.+ C 
& in 
C = 0 
t 
2 
So, nodia.xt = & 2 
x = 
www.© Sol. 6 Option (C) is correct. 
1 
f (z) z 1 z 
3 
= 2 + - + 
1 
C p # = sum of the residues of the poles which lie 
2 j f (z)dz 
inside the given closed region. 
C & z + 1 = 1 
Only pole z =- 1 inside the circle, so residue at z =- 1 is. 
f (z) 
- + 
z 
1 3 
= 1 + + 
(z ) (z ) 
z z 
1 1 
( )( ) 
= + + 
( )( ) 
lim 
z z 
1 3 
2 2 
1 
z 1 
+ - + = = 
"- 
1 
C p # = 1 
So 2 j f (z)dz 
Sol. 7 Option (A) is correct. 
= p + p 
x = -1 = i cos 2 i sin 2 
So, x = ei 2p 
= 2p ^ h & ei i 
xx ei x 
^ h = e 2-p 
2 p 
Sol. 8 Option (D) is correct. 
d y t 
dy t 
( ) ( ) 
( ) 
dt 
dt 
y t 
2 
2 
2 
+ + = d(t) 
By taking Laplace transform with initial conditions 
0 dy 2 sy s y 0 Y s 
- - + - + 
; E = 1 
s Y(s) sy( ) dt [ ( ) ( )] ( ) 
t 
2 
0 
= 
& 6s2Y(s) + 2s - 0@+ 26sY(s) + 2@+ Y(s) = 1 
Y(s) [s2+ 2s + 1] = 1 - 2s - 4 
Y(s) 
- - 
s 
2 1 
2 3 
2 = 
+ + 
s s 
We know that, If, y(t) Y(s) L
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
then, 
dy t 
( ) 
dt 
sY(s) y(0) L - 
So, sY(s) - y(0) 
- - + 
s s 
2 1 
2 3 
( ) 
s s 
2 2 = 
+ + 
( ) 
2 2 
- s - s + s + s 
+ 
2 3 2 4 2 
2 
+ + 
(s 2 s 1 
) 
= 
sY(s) - y(0) 
s 
s 
+ 2 
= 
+ 1 
+ 
1 
2 2 2 = 
+ 
+ 
+ 
(s 1 ) ( s 
1 
) ( s 
1 
) 
1 
1 
2 = + + 
s 1 (s + 
1 
) 
Taking inverse Laplace transform 
dy t 
( ) 
dt 
= e-tu(t) + te-tu(t) 
dy 
At t = 0+, dt 
t=0+ 
= e0+ 0 = 1 
Sol. 9 Option (A) is correct. 
Divergence of A in spherical coordinates is given as 
1 1 in 
r A 
krn 
2 co.r 
2 
nodia.www.© = 2 ( ) 
d:A ( ) 
r r 
2 
2 
= 2 + 
r r 
2 
2 
k n 2 rn 
2 
= ( + ) 
+1 
r 
= k(n + 2)rn-1 = 0 (given) 
n + 2 = 0 & n =- 2 
Sol. 10 Option (C) is correct. 
Probability of appearing a head is 1/2. If the number of required tosses is odd, 
we have following sequence of events. 
H, TTH, TTTTH, ........... 
1 
1 
3 1 5 
= +b l +b l + 
Probability P 2 2 
2 
..... 
P 
2 
1 
1 1 
3 
4 
2 
= 
- 
= 
Sol. 11 Option (B) is correct. 
f (x) = x3- 9x2+ 24x + 5 
( ) 
dx 
df x 
= 3x2- 18x + 24 = 0 
& 
df x 
( ) 
dx 
= x2- 6x + 8 = 0 x = 4, x = 2 
d f x 
( ) 
dx 
2 
2 
= 6x - 18 
For x = 2, 
d f x 
( ) 
dx 
12 18 6 < 0 2 
2 
= - =- 
So at x = 2, f (x) will be maximum 
f (x) 
max 
= (2)3- 9(2)2+ 24(2) + 5 
= 8 - 36 + 48 + 5 = 25
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 12 Option (B) is correct. 
Characteristic equation. 
A- lI = 0 
5 
2 
- - - 
l 3 
- = 0 
l 
5l + l2+ 6 = 0 
l2+ 5l + 6 = 0 
Since characteristic equation satisfies its own matrix, so 
A2+ 5A+ 6 = 0 & A2 =- 5A- 6I 
Multiplying with A 
A3+ 5A2+ 6A = 0 
A3+ 5(- 5A- 6I) + 6A = 0 
A3 = 19A+ 30I 
co.in 
nodia.www.© Sol. 13 Option (D) is correct. 
From Divergence theorem, we have 
###4v $ Avdv A n ds 
= # v $ t 
s 
The position vector 
rv = ^utx x + utyy + utz zh 
Here, Av = 5rv, thus 
= ct + t + t 2 m ^t + t + t h 
4$ Av u 
2 
x y z ux x uyy uz z : 
2 
x 
u 
y 
u 
z 
2 
2 
2 
= c dx 
+ + dz m = 3#5 = 15 
dy 
dx dy 
dz 
5 
## v $ t = ### 15dv = 15V 
So, 5r nds 
s 
Sol. 14 Option (C) is correct. 
dy = ky 
We have dx 
# dy = # k dx + A 
Integrating y 
or lny = kx + A 
Since y(0) = c thus lnc = A 
So, we get, lny = kx + lnc 
or lny = lnekx + lnc 
or y = cekx 
Sol. 15 Option (A) is correct. 
C R Integrals is 
# - + where C is circle z = 1 
z dz 
4 5 
3 4 
z z 
C 
2+ + 
f (z)dz 
C # 
= 0 if poles are outside C. 
Now z 2+ 4z + 5 = 0 
(z + 2)2+ 1 = 0 
Thus z1,2 2 j z1,2 > 1 =- ! & 
So poles are outside the unit circle.
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 16 Option (C) is correct. 
We have f (x) = x + x - 3 = 0 
fl(x) 
x 
= 1 
+ 1 
2 
Substituting x0 = 2 we get 
fl(x0) = 1.35355 and f (x0) = 2 + 2 - 3 = 0.414 
Newton Raphson Method 
x1 
f x 
( ) 
= - 0 
f x 
( ) 
x 
0 
0 
l 
Substituting all values we have 
= - 0 414 = 1.694 
2 . 1 3535 
x 1 . 
Sol. 17 Option (B) is correct. 
Writing A:B we have 
: 
: 
: 
1 
1 
1 
1 
4 
4 
1 
6 
6 
20 
SSSS 
WWWW 
l m 
co.in 
nodia.www.© R 
T 
V 
X 
Apply R3 R3 R2 " - 
: 
: 
: 20 
1 
1 
0 
1 
4 
0 
1 
6 
6 
6 
20 
l - m - 
R 
SSSS 
T 
V 
WWWW 
X 
For equation to have solution, rank of A and A:B must be same. Thus for no 
solution; l = 6, m ! 20 
Sol. 18 Option (C) is correct. 
Total outcome are 36 out of which favorable outcomes are : 
(1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 3), (2, 4), (2, 5), (2, 6); 
(3, 4), (3, 5), (3, 6), (4, 5), (4, 6), (5, 6) which are 15. 
Thus P(E) . 
= No of favourable outcomes 
= = 5 
. 
No of total outcomes 
15 
36 
12 
Sol. 19 Option (C) is correct. 
Eigen value of a Skew-symmetric matrix are either zero or pure imaginary in 
conjugate pairs. 
Sol. 20 Option (C) is correct. 
For a function x(t) trigonometric fourier series is 
3 
= / 
= + w + w 
x(t) Ao [An cosn t Bn sinn t] 
n 1 
Where, Ao T1 x(t)dt 
= # T0" fundamental period 
0T 
0 
An = T2 # x(t)cosn w 
t dt 
0T 
0 
Bn = T2 # x(t) sinn w 
t dt 
0T 
0 
For an even function x(t),Bn = 0 
Since given function is even function so coefficient Bn = 0, only cosine and constant
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
terms are present in its fourier series representation. 
Constant term : 
3 T 
4 A0 = 
T1 x(t)dt 
4 
- # 
T 
/ 
/ 
T1 T 
Adt 2Adt 
= / 
+ 3 4 - 
-: # # D 
T 
/ 
T 
/ 
T 
/ 
4 
4 
4 
1 TA AT 
= : 2 - 2 2 D A2 
T 
=- 
Constant term is negative. 
Sol. 21 Option (D) is correct. 
Given differential equation 
2 
d n x 
n x 
( ) ( ) 
dx 
2 - = 0 
L 
2 
Let n(x) = Aelx 
l 
x 
in 
So, A l 2 
e 
l x - 
Ae 
= 0 
L 
2 l 2 - 1 
= l =!co.0 & L1 
L 
2 Boundary condition, nodia.n ( 3 ) = 0 so take l =- 
n ( x ) = Ae - 
n(0) = Ae0 = K & A = K 
So, www.n(x) = Ke-(x/L) 
L x 
L © 1 
Sol. 22 Option (A) is correct. 
1 = 
Given that ey x x 
1 = 
or ln ey ln x x 
or y = x1 lnx 
Now dx 
dy ln x x x x 1 1 
= + ^- - 1 
ln 
x 
2h 1 
2 2 = - 
x x 
For maxima and minima : 
dy (1 ln ) 0 
dx 
1 x 
2 = - = 
x 
lnx = 1 " x = e 1 
Now 
d y 
dx 
2 
2 
=- 2 - ln 
x 
x 
3 b- 2 l- 1 1 
x 3 x 2 b x 
l 
=- 2 + 2 ln 
- 
1 
2 3 3 x x 
x 
x 
d x 
dy 
atx e 
2 
2 
= 1 
2 2 1 < 0 2 3 3 = - + - 
e e e 
So, y has a maximum at x = e1 
Sol. 23 Option (D) is correct. 
According to given condition head should comes 3 times or 4 times 
4 1 
1 
P(Heads comes 3 times or 4 times) C 2 C 
1 
2 
2 
4 
4 
4 
3 
3 
= b l + b l b l 
1 16 
= : + : : = 5 
1 4 1 
8 
1 
2 
16
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 24 Option (C) is correct. 
A v 
= t + 2 t 
dvl = dxatx + dyaty 
xyax x ay 
# A v : dl 
v (xyax x ay) (dxa dya ) 
C 
= # t + 2 t : t + t 
C 
x y 
= # + 2 
(xydx x dy) 
C 
xdx xdx dy dy 3 3 4 
3 
= # 2 3 + # 1 3 
+ # + # 
= 1 
: - D+ : - D+ - + 1 1 - 3 
= 1 
3 4 
1 
3 
3 
- 
= 1 2 - - 
© www.nodia.co.in 
1 
/ 
/ 
/ 
/ 
2 3 
1 
3 
3 
1 
1 3 
2 3 
2 
[ ] [ ] 
1 
3 4 
3 4 
3 1 3 
Sol. 25 Option (C) is correct. 
Given function 
X(z) 
z ( z z z 
1 ) ( 2 
) Poles are located at z = 0, z = 1, and z = 2 
At Z = 0 residues is 
= : 
R0 z Z 
zX ( ) = 
0 
- 2 
= 1 2#0 - - 
(0 1) (0 2) 
= 1 
Z 
at z = 1 , R1 = ( Z - 1) : 
X ( ) Z= 
1 
- = 
= 1 2#1 1 - 
1(1 2) 
At z = 2, R2 (z 2) X(z) 
z 2 
= - : 
= 
= 1 2 # 2 
3 - 
2(2 1) 
2 
- =- 
Sol. 26 Option (B) is correct. 
Taking step size h = 0.1, y(0) = 0 
x y 
dy = x + y y y hdx 
dx 
dy 
i+1 = i + 
0 0 0 y1 = 0 + 0.1(0) = 0 
0.1 0 0.1 y2 = 0 + 0.1(0.1) = 0.01 
0.2 0.01 0.21 y3 = 0.01 + 0.21#0.1 = 0.031 
0.3 0.031 
From table, at x = 0.3,y(x = 0.3) = 0.031 
Sol. 27 Option (D) is correct. 
Given that 
f (t) 
- s 
+ ; E 
L 1 3 1 
3 2 = 
+ + - 
s 4 s (K 3 
)s 
limf (t) 
t"3 
= 1 
By final value theorem 
limf (t) 
t"3 
= = 
limsF(s) 1 
s " 
0 
or 
: 
+ 
s ( 3 s 
1 
) 
4 3 
+ + - 
( ) 
lim 
s 0 3 2 
s s K s 
" 
= 1
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
or 
+ 
s ( 3 s 
1 
) 
4 3 
s 0 s s 2+ s + K 
- 
[ ( )] 
lim 
" 
= 1 
1- 
K 3 
= 1 
or K = 4 
Sol. 28 Option (B) is correct. 
The highest derivative terms present in DE is of 2nd order. 
Sol. 29 Option (C) is correct. 
Number of elements in sample space is 210. Only one element 
"H,H,T,T,T,T,T,T,T,T, is event. Thus probability is 
1 
10 
2 
Sol. 30 Option (C) is correct. 
We have 
f (z) = c0 + c1z 
-1 
in 
1 + f ( z 
) 
- 
1 
f1(z) 
= = 1 + co.c0 + c1z 
z 
z 
nodia.www.© = z ( 1 + c 0 ) 
+ c 
1 
z 
2 
Since f1(z) has double pole at z = 0, the residue at z = 0 is 
Res f1(z)z=0 limz .f (z) 
z 0 
2 
= 1 
" 
= + 0 + 1 
. 
c m = c1 
" z ( 1 c ) 
c 
lim z 
z 
z 0 
2 
2 
Hence 
f1(z)dz 
# 
unit circle 
= # [ 1 
+ f ()] 
z 
dz 
= 2pj [Residue at z = 0] 
z 
unit circle 
= 2pjc1 
Sol. 31 Option (D) is correct. 
We have f (x) sin 
x 
x 
p 
= 
- 
Substituting x - p = y ,we get 
f (y + p) 
= sin( y 
+ p ) =- sin 
y (sin ) 
y 
y 
= -1 y 
y 
3 5 
1 y y y 
= - c - + - m 
! ! 
... 
y 
3 5 
or f (y + p) 
2 4 
1 y y ... 
=- + - + 
3 5 
! ! 
Substituting x - p = y we get 
f (x) 
=- + ( - p ) 
2 - - p 4 + 
! 
( ) 
! 
... 
x x 
1 
3 5 
Sol. 32 Option (A) is correct. 
(A) 
dy 
dx 
= y 
x 
or 
# dy 
y 
= # dx 
x 
or log y = log x + log c 
or y = cx Straight Line 
Thus option (A) and (C) may be correct. 
(B) 
dy 
dx 
=-y 
x
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
or 
# dy 
y 
=- # dx 
x 
or log y =- log x + log c 
or log y = log 1 + log 
c 
x 
or y 
x c 
= Hyperbola 
Sol. 33 Option (D) is correct. 
Sum of the principal diagonal element of matrix is equal to the sum of Eigen 
values. Sum of the diagonal element is -1 - 1 + 3 = 1.In only option (D), the 
sum of Eigen values is 1. 
Sol. 34 Option (C) is correct. 
The product of Eigen value is equal to the determinant of the matrix. Since one 
of the Eigen value is zero, the product of Eigen value is zero, thus determinant 
of the matrix is zero. 
Thus p11p22- p12p21 = 0 
© www.nodia.co.in 
Sol. 35 Option (B) is correct. 
The given system is 
x 
y 
4 
2 
2 
= 1G= G 
7 
= =6G 
We have A 
4 
2 
2 
= = 1G 
and A 
4 
2 
2 
= 1 = 0 Rank of matrix r(A) < 2 
Now C 
4 
2 
2 
1 
7 
= = 6G Rank of matrix r(C) = 2 
Since r(A) ! r(C) there is no solution. 
Sol. 36 Option (A) is correct. 
sinz can have value between -1 to +1. Thus no solution. 
Sol. 37 Option (A) is correct. 
We have f (x) = ex + e-x 
For x > 0, ex > 1 and 0 < e-x < 1 
For x < 0, 0 < ex < 1 and e-x > 1 
Thus f (x) have minimum values at x = 0 and that is e0+ e-0 = 2. 
Sol. 38 Option (A) is correct. 
sin x 
3 5 
x x x ... 
= + + + 
3 5 
! ! 
cos x 
2 4 
1 x x ... 
= + + + 
2 4 
! ! 
Thus only sin(x3) will have odd power of x . 
Sol. 39 Option (B) is correct. 
We have 
dx t 
( ) 
( ) 
dt 
+ 3x t = 0 
or (D + 3)x(t) = 0 
Since m =- 3, x(t) = Ce-3t Thus only (B) may be solution.
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 40 Option (C) is correct. 
We have x = e-x 
or f (x) = x - e-x 
f'(x) = 1 + e-x 
The Newton-Raphson iterative formula is 
xn+1 
f x 
( ) 
= - n 
f x 
'( ) 
x 
n 
n 
x= - - n 
Now f (xn) xn e 
f'(xn) 1 e x= + - n 
x 
- 
- 
x e 
1 n x 
n = - 
Thus xn+1 x 
e 
n 
n 
+ 
- 
x e 
1 
+ 
( ) 
n 
e 
1 
x 
x 
n 
n 
= 
+ 
- 
- 
Sol. 41 Option (A) is correct. 
1 
d n 
- 
1 
Res f (z)( z in 
a ) n 
z=a 
( n 1 
)! 
co.f () 
z 
dz 
n 
nodia.www.© 1 z a 
= 
- 
- - 
= 6 @ 
Here we have n = 2 and a = 2 
Thus Res f (z)z=2 
1 2 
( )! 
d z 
( ) 
1 
; E 
dz ( ) ( ) 
2 1 z z 
2 2 
z a 
2 
2 2 = 
- 
- 
- + = 
d 
1 
; E 
dz ( z 2 
) 
z a 
2 = 
+ = 
2 
- 
(z 2) 
z a 
3 = 
+ 
= 
; E 
=- 2 32 
64 
=- 1 
Sol. 42 Option (D) is correct. 
eP = L-1 (sI -A)-1 6 @ 
- 
L 
s 
0 s 
0 0 
2 
1 
3 
1 
1 
= - - - 
- 
e= G = Go 
L 
s 
2 s 
1 
3 
1 
1 
= 
- 
+ 
- 
- 
e= G o 
s 
3 
+ 
L ( )( ) 
2 
- 
( )( ) 
1 
( )( ) 
( )( ) 
s s 
s s 
s s 
s 
s s 
1 1 2 
1 2 
1 2 
1 2 
= - + + 
+ + 
+ + 
+ + 
f> Hp 
1 - 
2 
1 2 
e e 
e e 
1 2 
e e 
e e 
2 
2 2 2 
= 1 2 
- + 
- 
- + 
- - 
- - 
- - 
= - - G 
Sol. 43 Option (B) is correct. 
Taylor series is given as 
x a 
f a x a f a "( ) ... 
f (x) ( ) 
! 
'( ) 
( ) 
! 
f a 
1 2 
2 
= + - + - + 
For x = p we have 
Thus f (x) ( ) 
f x f "( )... 
! 
'( ) 
( ) 
! 
x 
f x 
1 2 
2 
= p + - p p + - p 
Now f (x) = ex + sinx 
f'(x) = ex + cos x 
f"(x) = ex - sinx 
f"(p) = ep - sinp = ep
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Thus the coefficient of (x - p)2 is 
p 
f"( ) 
2 
! 
Sol. 44 Option (A) is correct. 
The equation of straight line from (0,0) to (1,2) is y = 2x . 
Now g(x,y) = 4x3+ 10y4 
or, g(x,2x) = 4x3+ 160x4 
1 
Now g(x,2x) 
1 # (4x3 160x4)dx 
0 
= # + 
0 
= [x4 + 32x5] 1 = 
33 
0 
Sol. 45 Option (B) is correct. 
Q 
= # + 
2 xdx 2 ydy 
I 2 (xdx ydy) 
P 
Q 
= # + # 
P 
2 xdx 2 ydy 0 
Q 
P 
= # + # = 
0 
1 
1 
0 
© www.nodia.co.in 
Sol. 46 Option (B) is correct. 
The given plot is straight line whose equation is 
x y 
-1 1 
+ = 1 
or y = x + 1 
Now I ydx 
1 
2 
= # (x 1)dx 
1 
2 
= # + 
(x ) 
2 
1 2 2 
= + 
; E . 
= 9 
- 4 = 2 5 
2 
2 
Sol. 47 Option (C) is correct. 
coth x 
= cosh 
x 
sinh 
x 
as x << 1, coshx . 1 and sinhx . x 
Thus coth x 
. 1 
x 
Sol. 48 Option (A) is correct. 
sin 
0 
lim 
^ q h 
2 
q" q 
q 
^ 
sin 
0 2 2 
^ 
h 
= lim 
2 
q" q 
h 
= lim 
2 
sin 
1 
2 
q" q 
0 2 
q 
^ 
^ 
h 
h 
= 1 = 0 . 
5 
2 
Sol. 49 Option (D) is correct. 
We have, lim 
1 
x"0 2 
x 
= 3 
lim x 
x 
2 
"3 
= 3 
lim e 
x 
x 
"3 
- = 3 
lim e 
x 
x2 
"3 
- = 0 
lim e 
x 
x 
0 
2 
" 
- = 1 Thus e x- 2 is strictly bounded. 
Sol. 50 Option (A) is correct. 
We have f (x) = e-x = e-(x - 2) - 2 = e-(x - 2)e-2 
x ... 
( ) 
( ) 
! 
x 
1 2 e 
2 
2 2 
= - - + - -2 ; E
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
= 1 - (x - 2) e-2 6 @ Neglecting higher powers 
= (3 - x)e-2 
Sol. 51 Option (D) is correct. 
We have k 
2 
2 d y 
dx 
2 
= y - y2 
or 
2 
d y 
dx 
y 
2 - 
k 
2 
y 
2 
=- 2 
k 
A.E. D 
2 1 
2 - = 0 
k 
or D 
=!1 
k 
C.F. = C1e - x 
x k 
+ 
C2e k 
P.I. 
= 
1 - y 2 
2 c 2 
m 
= in 
y 
D - 
1 k 
2 
2 
k 
2 
Thus solution is 
co.y = C1e - x 
x k 
+ C2e k 
+ 
y2 From y(0) = y1 we get 
C1+ nodia.C2 = y1- y2 
From y(3) = y2 we get that C1 must be zero. 
Thus www.C2 = y1- y2 
y = (y1 - y2)e - x k 
+ 
y2 © Sol. 52 Option (B) is correct. 
We have 
f (x) = x3- x2+ 4x - 4 
f'(x) = 3x2- 2x + 4 
Taking x0 = 2 in Newton-Raphosn method 
x1 
f x 
( ) 
= - 0 
'( ) 
x 
f x 
0 
0 
3 2 
- + - 
2 2 42 4 
( ) 
2 
( ) ( ) 
2 
3 2 2 2 4 
= - 
- + 
3 4 
= 
Sol. 53 Option (C) is correct. 
For two orthogonal signal f (x) and g(x) 
# + f (x)g(x)dx 
= 0 
3 
3 
- 
i.e. common area between f (x) and g(x) is zero. 
Sol. 54 Option (A) is correct. 
We know that 
# 1 
ds 
= 2pj [sum of residues] 
s 
2 - 1 
D 
Singular points are at s =!1 but only s =+ 1 lies inside the given contour, 
Thus Residue at s =+ 1 is 
- 
lim(s 1) f (s) 
s " 
1 
lim(s ) 
s 
1 
1 
1 
1 
2 
s 1 2 = - 
- 
= 
" 
# 1 
ds 
2 j j 
s 
2 - 1 
D 
= p ` 1 j = p 
2
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 55 Option (C) is correct. 
For two orthogonal vectors, we require two dimensions to define them and 
similarly for three orthogonal vector we require three dimensions to define them. 
2M vectors are basically M orthogonal vector and we require M dimensions to 
define them. 
Sol. 56 Option (A) is correct. 
We have 
f (x) = x2- x + 2 
f'(x) = 2x - 1 = 0 x 
" = 1 
2 
f"(x) = 2 
Since f"(x) = 2 > 0, thus x 
= 1 is minimum point. The maximum value in 
2 
closed interval 6-4,4@ will be at x =- 4 or x = 4 
Now maximum value 
= max[f (- 4), f (4)] 
= max(18,10) 
= 18 
© www.nodia.co.in 
Sol. 57 Option (C) is correct. 
Probability of failing in paper 1 is P(A) = 0.3 
Possibility of failing in Paper 2 is P(B) = 0.2 
Probability of failing in paper 1, when 
student has failed in paper 2 is P 0.6 B 
^A h = 
We know that 
A b l 
P B 
P + B = 
( ) 
P B 
( ) 
= bAl = 0.6 # 0.2 = 0.12 
or P(A + B) P(B)P B 
Sol. 58 Option (C) is correct. 
We have 
A 
R 
1 
1 
1 
1 
1 
1 
1 
0 
1 
SSSS V 
1 
1 
0 
1 
1 
0 
1 
0 
0 
SSSS 
WWWW 
= - + - 
T 
R 
T 
X 
V 
WWWW 
X 
R3- R1 
Since one full row is zero, r(A) < 3 
Now 
1 
1 
1 
-1 =- 2 ! 0, thus r(A) = 2 
Sol. 59 Option (D) is correct. 
The vector Triple Product is 
A# (B #C) = B(A$ C) -C(A$ B) 
Thus 4#4#P =4 (4$ P) - P(4$4) =4 (4$ P) -42P 
Sol. 60 Option (A) is correct. 
The Stokes theorem is 
## (4# F) $ ds = # A $ dl 
Sol. 61 Option (C) is correct.
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
3 
-# = 1 
We know p(x)dx 
3 
3 -a 
-# = 1 
Thus Ke x dx 
3 
0 
# a + # 3 
-a 
= 1 
- or Ke x dx Ke x dx 
0 
3 
or 
K e x 0 k e x 
a a 0 3+ - 
6 a @ 6 - a @ 3 
= 1 
( ) 
- 
or K K 
a + a = 1 
or K 
2 a 
= 
Sol. 62 Option (A) is correct. 
We have xo (t) + 2x(t) = s(t) 
Taking Laplace transform both sides 
sX(s) - x(0) + 2X(s) = 1 
co.in 
nodia.www.© or sX(s) + 2X(s) = 1 Since x(0-) = 0 
X(s) 
= 1 
+ 
s 2 
Now taking inverse Laplace transform we have 
x(t) = e-2tu(t) 
Sol. 63 Option (A) is correct. 
Sum of the Eigen values must be equal to the sum of element of principal diagonal 
of matrix. 
Only matrix 
6 
2 
2 
= 6G satisfy this condition. 
Sol. 64 Option (B) is correct. 
We have W = lnz 
u + jv = ln(x + jy) 
or eu+jv = x + jy 
or eu ejv = x + jy 
eu (cos v + j sinv) = x + jy 
Now x = eu cos v and y = eu sinv 
Thus x2+ y2 = e2u Equation of circle 
Sol. 65 Option (D) is correct. 
We have 
z 
dz 
4 
1 
z j 
2 
# 
2 + - = 
1 
(z i) (z i) 
dz 
2 2 
# 
z j 2 
= 
+ - 
- = 
P(0,2) lies inside the circle z - j = 2 and P(0, - 2) does not lie. 
Thus By cauchy’s integral formula 
= p - 
I ( ) 
1 
" + - 
( )( ) 
i lim z i 
z i z i 
2 2 
2 2 
z 2i 
= p p 
# 2 
i 
= 
i i 
2 2 
2 
C 
+ 
Sol. 66 Option (C) is correct. 
= q q p # 
I sin3 d 
0
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
= # p ` 3 sin q - sin 3 
q j d 
q 
sin3q = 3 sinq - 4 sin3q 
4 
0 
= - q = w q 
p p 
3 
s 
4 
cos 3 
: D : D 
12 
0 0 
4 3 
4 3 
1 
12 
1 
12 
y a k 
P y+d 
= 
( ) 
P d 
= 0 006 = 0 4 
. . 
0 015 
© www.nodia.co.in 
3 4 
= 8 + B-8 + B= 
Sol. 67 Option (D) is correct. 
Let d " defective and y " supply by Y 
p d 
( ) 
P(y + d) = 0.3 # 0.02 = 0.006 
P(d) = 0.6 # 0.1 + 0.3 # 0.02 + 0.1 # 0.03 = 0.015 
P d 
y a k 
. 
Sol. 68 Option (C) is correct. 
We have A 
4 
2 
2 
= = 4G 
Now 6A - lI @[X] = 0 
or 
- 
= - G= G 
4 
2 
2 
4 
101 
101 
l 
l 
0 
= =0G 
or (101)(4 - l) + 2(101) = 0 
or l = 6 
Sol. 69 Option (A) is correct. 
We have 
2 
d y k y 2 
dx 
+ 2 = 0 
or D2y + k2y = 0 
The AE is m2+ k2 = 0 
The solution of AE is m =!ik 
Thus y = Asinkx + Bcos kx 
From x = 0, y = 0 we get B = 0 and x = a,y = 0 we get 
Asinka = 0 
or sinka = 0 
k 
= mpx 
a 
=/ ` p j 
Thus y A sin 
m x 
a 
m 
m 
Sol. 70 Option (A) is correct. 
We have f (x) 
e 
1 e 
x 
x 
= 
+ 
For x " 3, the value of f (x) monotonically increases. 
Sol. 71 Option (B) is correct. 
Order is the highest derivative term present in the equation and degree is the 
power of highest derivative term. 
Order = 2, degree = 1 
Sol. 72 Option (D) is correct. 
Probability of coming odd number is 2 1 
and the probability of coming even number 
is 2 1 
. Both the events are independent to each other, thus probability of coming
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
odd number after an even number is 2 1 
# = 1 . 
2 1 
4 
Sol. 73 Option (B) is correct. 
We have 
2 
d y 
dx 
5 dy 6y 2 
- + = 0 
dx 
The A.E. is m2- 5m + 6 = 0 
m = 3,2 
The CF is yc = C 3 
x 2 
x 
1 
e + C 2 
e Since Q = 0, thus y = C e x + C e 2 
x 
1 
3 
2 
Thus only (B) may be correct. 
Sol. 74 Option (A) is correct. 
We have f (t) = e(a+2)t+5 = e5.e(a+2)t 
Taking Laplace transform we get 
F(s) 
= 5 1 
co.in 
nodia.www.© ; - + E Thus Re(s) > (a + 
2) ( ) 
e 
s a 2 
Sol. 75 Option (C) is correct. 
For x > 0 the slope of given curve is negative. Only (C) satisfy this condition. 
Sol. 76 Option (C) is correct. 
Newton - Raphson " Method-Solving nonlinear eq. 
Runge - kutta Method " Solving ordinary differential eq. 
Simpson’s Rule " Numerical Integration 
Gauss elimination " Solving linear simultaneous eq. 
Sol. 77 Option (C) is correct. 
We have A 
- 
= G 
4 
4 
2 
= 3 
Characteristic equation is 
A - lI = 0 
or 
4 
4 
2 
3 
l 
l 
- 
- = 0 
or (- 4 - l)(3 - l) - 8 = 0 
or -12 + l + l2- 8 = 0 
or l2+ l - 20 = 0 
or l =- 5,4 Eigen values 
Eigen vector for l =- 5 
- l = 0 
( ) A I Xi 
1 - ( - 
5 
) 2 
x 
= 4 
8 - 4 
G= x 
G 
1 
2 
0 
= =0G 
x 
x 
1 
0 
2 
0 
1 
2 
= =G G 
0 
= =0G R2- 4R1 
x1+ 2x2 = 0 
Let -x1 = 2 & x2 =- 1, 
Thus X 
2 
= =-1G Eigen vector
GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 
Sol. 78 Option (A) is correct. 
We have 
A 
- 
2 . 
0 
0 1 
= G and A 
= 3 
1 2 1 
a 
0 b 
- = = G 
Now AA-1 = I 
or 
0 1 
3 0 2 1 
. a 
= =G G 
b 
2 
0 
- 
1 
0 
0 
= = 1G 
or 
- 
a . b 
2 01 
= G 
b 
1 
0 
3 
1 
0 
0 
= = 1G 
or 2a - 0.1 = 0 and 3b = 1 
Thus solving above we have b 
= 1 and a 
3 
= 1 
60 
Therefore a + b 
= 1 
+ = 7 
3 
1 
60 
20 
Sol. 79 Option (A) is correct. 
Gaussian PDF is 
1 (x co.) 
in 
nodia.www.© -m # for -3 # x # 3 
3 - 
- 
f (x) e dx 
2 
2 2 
2 
p s 
= 
3 
s 
3 
-# = 1 
and f (x)dx 
3 
Substituting m = 0 and s = 2 in above we get 
1 x 
-# 3 - 
2 
e dx 
= 1 
2 2 
8 
p 3 
1 
2 
or 2 e dx 
2 2 
0 
x 
8 
p 
# 3 - = 1 
1 
2 
or e dx 
2 
0 
x 
8 
p 
# 3 - = 1 
Sol. 80 Option (C) is correct. 
From orthogonal matrix 
[AAT] = I 
Since the inverse of I is I , thus 
[AAT]-1 = I-1 = I 
*********

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  • 1. No part of this publication may be reproduced or distributed in any form or any means, electronic, mechanical, photocopying, or otherwise without the prior permission of the author. GATE SOLVED PAPER Electronics & Communication Engineering Mathematics Copyright © By NODIA & COMPANY Information contained in this book has been obtained by authors, from sources believes to be reliable. However, neither Nodia nor its authors guarantee the accuracy or completeness of any information herein, and Nodia nor its authors shall be responsible for any error, omissions, or damages arising out of use of this information. This book is published with the understanding that Nodia and its authors are supplying information but are not attempting to render engineering or other professional services. NODIA AND COMPANY B-8, Dhanshree Tower Ist, Central Spine, Vidyadhar Nagar, Jaipur 302039 Ph : +91 - 141 - 2101150 www.nodia.co.in email : enquiry@nodia.co.in
  • 2. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 2013 ONE MARK Q. 1 The maximum value of q until which the approximation sinq . q holds to within 10% error is (A) 10c (B) 18c (C) 50c (D) 90c Q. 2 The minimum eigen value of the following matrix is R 3 5 2 5 12 7 2 7 5 SSSS WWWW © www.nodia.co.in T V X (A) 0 (B) 1 (C) 2 (D) 3 4 Q. 3 A polynomial f (x) a4x a 3 x a x a x a 3 2 2 = + + + 1 - 0 with all coefficients positive has (A) no real roots (B) no negative real root (C) odd number of real roots (D) at least one positive and one negative real root 2013 TWO MARKS Q. 4 Let A be an m#n matrix and B an n#m matrix. It is given that determinant ^Im + ABh = determinant ^In + BAh, where Ik is the k#k identity matrix. Using the above property, the determinant of the matrix given below is 2 1 1 1 1 2 1 1 1 1 2 1 1 1 1 2 R SSSSS S T V WWWWW W X (A) 2 (B) 5 (C) 8 (D) 16 2012 ONE MARK Q. 5 With initial condition x(1) = 0.5, the solution of the differential equation t dx dt + x = t , is (A) x t 2 = - 1 (B) x = t 2- 1 2 = (D) x t2 (C) x t 2 2 =
  • 3. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS = 1 2 + - + . Q. 6 Given f (z) z 1 z 3 If C is a counter clockwise path in the z -plane such that z + 1 = 1, the value of 1 2 j f (z)dz C p # is (A) -2 (B) -1 (C) 1 (D) 2 Q. 7 If x = -1, then the value of xx is (A) e-p/2 (B) ep/2 (C) x (D) 1 2012 TWO MARKS © www.nodia.co.in Q. 8 Consider the differential equation d y t dy t 2 y t 2 ( ) ( ) ( ) dt dt 2 dy + + = d(t) with y(t) =- 2 and dt = 0 t t 0 0 = = - - dy The numerical value of dt t=0+ is (A) -2 (B) -1 (C) 0 (D) 1 Q. 9 The direction of vector A is radially outward from the origin, with A = krn . where r2 = x2+ y2+ z2 and k is a constant. The value of n for which d:A = 0 is (A) -2 (B) 2 (C) 1 (D) 0 Q. 10 A fair coin is tossed till a head appears for the first time. The probability that the number of required tosses is odd, is (A) 1/3 (B) 1/2 (C) 2/3 (D) 3/4 Q. 11 The maximum value of f (x) = x3- 9x2+ 24x + 5 in the interval [1,6] is (A) 21 (B) 25 (C) 41 (D) 46 Q. 12 Given that - - > H = > H, the value of A3 is 5 2 3 0 A and I 1 0 0 = 1 (A) 15A+ 12I (B) 19A+ 30I (C) 17A+ 15I (D) 17A+ 21I 2011 ONE MARK Q. 13 Consider a closed surface S surrounding volume V . If rv is the position vector of a ## v $ t point inside S , with nt the unit normal on S , the value of the integral 5r n dS S is (A) 3V (B) 5V (C) 10V (D) 15V
  • 4. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS dy = ky y = c is Q. 14 The solution of the differential equation dx , (0) (A) x = ce-ky (B) x = kecy (C) y = cekx (D) y = ce-kx Q. 15 The value of the integral # - + where c is the circle z = 1 is given z dz 4 5 3 4 2+ + (z z ) by c (A) 0 (B) 1/10 (C) 4/5 (D) 1 2011 TWO MARKS Q. 16 A numerical solution of the equation f (x) + x - 3 = 0 can be obtained using Newton- Raphson method. If the starting value is x = 2 for the iteration, the value of x that is to be used in the next step is (A) 0.306 (B) 0.739 (C) 1.694 (D) 2.306 © www.nodia.co.in Q. 17 The system of equations + + = + + = + + = x y z x y y x y z 6 4 6 20 4 l m has NO solution for values of l and μ given by (A) l = 6, m = 20 (B) l = 6, m =Y 20 (C) l =Y 6, m = 20 (D) l =Y 6, m = 20 Q. 18 A fair dice is tossed two times. The probability that the second toss results in a value that is higher than the first toss is (A) 2/36 (B) 2/6 (C) 5/12 (D) 1/2 2010 ONE MARKS Q. 19 The eigen values of a skew-symmetric matrix are (A) always zero (B) always pure imaginary (C) either zero or pure imaginary (D) always real Q. 20 The trigonometric Fourier series for the waveform f (t) shown below contains (A) only cosine terms and zero values for the dc components
  • 5. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS (B) only cosine terms and a positive value for the dc components (C) only cosine terms and a negative value for the dc components (D) only sine terms and a negative value for the dc components Q. 21 A function n(x) satisfied the differential equation 2 d n x n x ( ) ( ) dx 2 - = 0 2 L where L is a constant. The boundary conditions are :n(0) = K and n(3) = 0. The solution to this equation is (A) n(x) = Kexp(x/L) (B) n(x) = Kexp(- x/ L) (C) n(x) = K2exp(- x/L) (D) n(x) = Kexp(- x/L) 2010 TWO MARKS © www.nodia.co.in Q. 22 If ey = x1/x , then y has a (A) maximum at x = e (B) minimum at x = e (C) maximum at x = e-1 (D) minimum at x = e-1 Q. 23 A fair coin is tossed independently four times. The probability of the event “the number of time heads shown up is more than the number of times tail shown up” (A) 1/16 (B) 1/3 (C) 1/4 (D) 5/16 v = t + 2 t , then A dl Q. 24 If A xyax x ay # v $ v over the path shown in the figure is C (A) 0 (B) 2 3 (C) 1 (D) 2 3 Q. 25 The residues of a complex function ( ) - ( )( ) x z z z z z 1 2 = 1 2 - - at its poles are (A) 1 2, - 1 2 and 1 (B) 1 2 , - 1 and -1 2 1 and 2 (C) 2, 1 -3 (D) , 2 1 - 1 and 2 3 Q. 26 Consider differential equation dy x ( ) dx ( ) - y x = x , with the initial condition y(0) = 0. Using Euler’s first order method with a step size of 0.1, the value of y(0.3) is (A) 0.01 (B) 0.031 (C) 0.0631 (D) 0.1
  • 6. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Q. 27 Given ( ) - 1 3 s + 1 ; E. If limf (t) 1 3 2 = + + - s 4 s k 3 s ( ) f t L t = "3 , then the value of k is (A) 1 (B) 2 (C) 3 (D) 4 2009 ONE MARK Q. 28 The order of the differential equation 2 3 + + 4 = - c m is d y dt dy y et dt 2 (A) 1 (B) 2 (C) 3 (D) 4 Q. 29 A fair coin is tossed 10 times. What is the probability that only the first two tosses will yield heads? (A) 2 10 1 c 1 m 2 (B) C 2 2 2 b l 1 10 c m (D) C 2 (C) 2 10 1 2 co.in nodia.www.© 10 b l = + -1, then Q. 30 If f (z) c0 c1z # + f z is given by ( ) z dz 1 unit circle (A) 2pc1 (B) 2p(1 + c0) (C) 2pjc1 (D) 2p(1 + c0) 2009 TWO MARKS Q. 31 The Taylor series expansion of sin x x - p at x = p is given by (A) + ( - p ) 2 + (B) ! ... x 1 3 - - ( - p ) 2 + ! ... x 1 3 (C) - ( - p ) 2 + (D) ! ... x 1 3 - + ( - p ) 2 + ! ... x 1 3 Q. 32 Match each differential equation in Group I to its family of solution curves from Group II Group I Group II A. dy dx = y 1. Circles x B. dy dx =-y 2. Straight lines x C. dy dx y x = 3. Hyperbolas D. dy dx y x =- (A) A - 2, B - 3,C - 3,D - 1 (B) A - 1, B - 3,C - 2,D - 1 (C) A - 2, B - 1,C - 3,D - 3 (D) A - 3, B - 2,C - 1,D - 2
  • 7. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Q. 33 The Eigen values of following matrix are R - - - 1 3 0 3 1 0 5 6 3 SSSS T V WWWW X (A) 3, 3 + 5j, 6 - j (B) -6 + 5j, 3 + j, 3 - j (C) 3 + j, 3 - j, 5 + j (D) 3, - 1 + 3j, - 1 - 3j 2008 ONE MARKS Q. 34 All the four entries of the 2 # 2 matrix P p p p p 11 21 12 22 = = G are nonzero, and one of its eigenvalue is zero. Which of the following statements is true? (A) p11p12- p12p21 = 1 (B) p11p22- p12p21 =- 1 (C) p11p22- p12p21 = 0 (D) p11p22+ p12p21 = 0 © www.nodia.co.in Q. 35 The system of linear equations 4x + 2y = 7 2x + y = 6 has (A) a unique solution (B) no solution (C) an infinite number of solutions (D) exactly two distinct solutions Q. 36 The equation sin(z) = 10 has (A) no real or complex solution (B) exactly two distinct complex solutions (C) a unique solution (D) an infinite number of complex solutions Q. 37 For real values of x , the minimum value of the function f (x) = exp(x) + exp(- x) is (A) 2 (B) 1 (C) 0.5 (D) 0 Q. 38 Which of the following functions would have only odd powers of x in its Taylor series expansion about the point x = 0 ? (A) sin(x3) (B) sin(x2) (C) cos (x3) (D) cos (x2) Q. 39 Which of the following is a solution to the differential equation dx t ( ) ( ) dt + 3x t = 0 ? (A) x(t) = 3e-t (B) x(t) = 2e-3t (C) x(t) =- 3 t 2 (D) x(t) = 3t2 2 2008 TWO MARKS Q. 40 The recursion relation to solve x = e-x using Newton - Raphson method is = n + (A) xn e x 1 - (B) x x e n n x = - n + 1 - - x = + e n n n 1 x (C) x (1 x ) + + - 1 n e (D) - - - x e ( 1 x ) 1 x + - x e n n x n x n 1 2 n n = - -
  • 8. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Q. 41 The residue of the function f (z) 1 2 2 = + - (z 2) (z 2) at z = 2 is (A) - 1 (B) 32 - 1 16 (C) 1 (D) 16 1 32 Q. 42 Consider the matrix P 0 2 1 = =- -3G. The value of ep is (A) - - - - 2 1 2 1 - - e e e e - - 1 2 2 1 - - e e e e 2 3 2 2 5 > - - H (B) - - - 1 1 1 2 + - e e e e - - 2 1 1 2 - + e e 2 3 2 > - - H 2 4 e e (C) - - - - 2 1 2 1 - - e e e e - - 1 2 2 1 - + e e e 5 2 6 3 4 6 > - - H (D) - - - - 1 - 2 1 2 e e e e - - 1 - 2 1 2 e e e e 2 2 2 2 > - - H - + - + © www.nodia.co.in Q. 43 In the Taylor series expansion of exp(x) + sin(x) about the point x = p, the coefficient of (x - p)2 is (A) exp(p) (B) 0.5 exp(p) (C) exp(p) + 1 (D) exp(p) - 1 Q. 44 The value of the integral of the function g(x,y) = 4x3+ 10y4 along the straight line segment from the point (0,0) to the point (1,2) in the x - y plane is (A) 33 (B) 35 (C) 40 (D) 56 Q. 45 Consider points P and Q in the x - y plane, with P = (1,0) and Q = (0,1). The Q # + along the semicircle with the line segment PQ as line integral 2 (xdx ydy) P its diameter (A) is -1 (B) is 0 (C) is 1 (D) depends on the direction (clockwise or anit-clockwise) of the semicircle 2007 ONE MARK Q. 46 The following plot shows a function which varies linearly with x . The value of the integral I ydx 1 2 = # is
  • 9. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS (A) 1.0 (B) 2.5 (C) 4.0 (D) 5.0 Q. 47 For x << 1, coth (x) can be approximated as (A) x (B) x2 (C) 1 (D) x 1 2 x q b l is sin 2 0 q Q. 48 lim q" (A) 0.5 (B) 1 (C) 2 (D) not defined Q. 49 Which one of following functions is strictly bounded? (A) 1/x2 (B) ex in (C) x2 co.(D) e - x2 nodia.www.© Q. 50 For the function e-x , the linear approximation around x = 2 is (A) (3 - x)e-2 (B) 1 - x (C) 63 + 3 2 - (1 - 2)x @e-2 (D) e-2 2007 TWO MARKS Q. 51 The solution of the differential equation k 2 d y y y dx 2 2 = - 2 under the boundary conditions (i) y = y1 at x = 0 and (ii) y = y2 at x = 3, where k,y1 and y2 are constants, is x y = 1- 2 a- 2 k+ 2 (A) y (y y )exp k x y = 2- 1 a- k+ 1 (B) y (y y )exp k x y = ^ 1- 2h a k+ 1 (C) y y y sinh k x y = ^ 1- 2h a- k+ 2 (D) y y y exp k Q. 52 The equation x3- x2+ 4x - 4 = 0 is to be solved using the Newton - Raphson method. If x = 2 is taken as the initial approximation of the solution, then next approximation using this method will be (A) 2/3 (B) 4/3 (C) 1 (D) 3/2 Q. 53 Three functions f1(t), f2(t) and f3(t) which are zero outside the interval [0, T] are shown in the figure. Which of the following statements is correct?
  • 10. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS © www.nodia.co.in (A) f1(t) and f2(t) are orthogonal (B) f1(t) and f3(t) are orthogonal (C) f2(t) and f3(t) are orthogonal D) f1(t) and f2(t) are orthonormal Q. 54 If the semi-circular control D of radius 2 is as shown in the figure, then the value of the integral # 1 ds is (s 2 - 1 ) D (A) jp (B) -jp (C) -p (D) p Q. 55 It is given that , ... X X XM 1 2 at M non-zero, orthogonal vectors. The dimension of the vector space spanned by the 2M vectors X1,X2,...XM, - X1, - X2,... - XM is (A) 2M (B) M+ 1 (C) M (D) dependent on the choice of , ,... X X XM 1 2 Q. 56 Consider the function f (x) = x2- x - 2. The maximum value of f (x) in the closed interval [- 4, 4] is (A) 18 (B) 10 (C) -225 (D) indeterminate Q. 57 An examination consists of two papers, Paper 1 and Paper 2. The probability of failing in Paper 1 is 0.3 and that in Paper 2 is 0.2. Given that a student has failed in Paper 2, the probability of failing in Paper 1 is 0.6. The probability of a student failing in both the papers is (A) 0.5 (B) 0.18 (C) 0.12 (D) 0.06
  • 11. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 2006 ONE MARK Q. 58 The rank of the matrix R 1 1 1 1 1 1 1 0 1 - SSSS T V WWWW X is (A) 0 (B) 1 (C) 2 (D) 3 Q. 59 4#4# P, where P is a vector, is equal to (A) P P 2P #4# -4 (B) 42P +4 (4# P) (C) 42P +4# P (D) 4(4$ P) -42P Q. 60 ## (4# P) $ ds , where P is a vector, is equal to (A) # P $ dl (B) # 4#4# P $ dl (C) # 4# P $ dl (D) ### 4$ Pdv © www.nodia.co.in Q. 61 A probability density function is of the form p(x) = Ke-a x ,x ! (-3,3). The value of K is (A) 0.5 (B) 1 (C) 0.5a (D) a Q. 62 A solution for the differential equation xo (t) + 2x(t) = d(t) with initial condition x(0-) = 0 is (A) e-2tu(t) (B) e2tu(t) (C) e-tu(t) (D) etu(t) 2006 TWO MARKS Q. 63 The eigenvalue and the corresponding eigenvector of 2 # 2 matrix are given by Eigenvalue Eigenvector l1 = 8 v 1 1 1 == G l2 = 4 v 1 1 2 = = G - The matrix is (A) 6 2 2 = 6G (B) 4 6 6 = 4G (C) 2 4 4 = 2G (D) 4 8 8 = 4G Q. 64 For the function of a complex variable W = lnZ (where, W = u + jv and Z = x + jy , the u = constant lines get mapped in Z -plane as (A) set of radial straight lines (B) set of concentric circles (C) set of confocal hyperbolas (D) set of confocal ellipses Q. 65 The value of the constant integral 1 # dz is positive sense is z 4 z j 2 2 + - = (A) j p (B) 2 2 p - - p (D) (C) j 2 2 p
  • 12. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS q q p # is given by Q. 66 The integral sin3 d 0 (A) 1 (B) 2 2 3 (C) 3 4 (D) 8 3 Q. 67 Three companies X,Y and Z supply computers to a university. The percentage of computers supplied by them and the probability of those being defective are tabulated below Company % of Computer Supplied Probability of being supplied defective X 60% 0.01 Y 30% 0.02 Z 10% 0.03 Given that a computer is defective, the probability that was supplied by Y is (A) 0.1 (B) 0.2 (C) 0.3 (D) 0.4 © www.nodia.co.in Q. 68 For the matrix 4 2 2 = 4G the eigenvalue corresponding to the eigenvector 101 =101G is (A) 2 (B) 4 (C) 6 (D) 8 Q. 69 For the differential equation 2 d y k y 0 2 dx + 2 = the boundary conditions are (i) y = 0 for x = 0 and (ii) y = 0 for x = a The form of non-zero solutions of y (where m varies over all integers) are (A) y A sin =/ m p x (B) y A cos a m m =/ p m x a m m = / m p (D) y Ame a (C) y Amx a m = / - p m x m Q. 70 As x increased from -3 to 3, the function f (x) e 1 e x x = + (A) monotonically increases (B) monotonically decreases (C) increases to a maximum value and then decreases (D) decreases to a minimum value and then increases 2005 ONE MARK Q. 71 The following differential equation has 2 3 2 c m+ c m + + = x 3 d y 4 dy y 2 2 dt dt (A) degree = 2, order = 1 (B) degree = 1, order = 2 (C) degree = 4, order = 3 (D) degree = 2, order = 3
  • 13. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Q. 72 A fair dice is rolled twice. The probability that an odd number will follow an even number is (A) 1/2 (B) 1/6 (C) 1/3 (D) 1/4 Q. 73 A solution of the following differential equation is given by © www.nodia.co.in d y dx 5 dy 6y 0 2 dx 2 - + = (A) y = e2x + e-3x (B) y = e2x + e3x (C) y = e-2x + 33x (D) y = e-2x + e-3x 2005 TWO MARKS Q. 74 In what range should Re(s) remain so that the Laplace transform of the function e(a+2)t+5 exits. (A) Re(s) > a + 2 (B) Re(s) > a + 7 (C) Re(s) < 2 (D) Re(s) > a + 5 Q. 75 The derivative of the symmetric function drawn in given figure will look like Q. 76 Match the following and choose the correct combination: Group I Group 2 E. Newton-Raphson method 1. Solving nonlinear equations F. Runge-kutta method 2. Solving linear simultaneous equations G. Simpson’s Rule 3. Solving ordinary differential equations H. Gauss elimination 4. Numerical integration 5. Interpolation 6. Calculation of Eigenvalues (A) E - 6, F - 1,G - 5, H - 3 (B) E - 1, F - 6,G - 4, H - 3 (C) E - 1, F - 3,G - 4, H - 2 (D) E - 5, F - 3,G - 4, H - 1 Q. 77 Given the matrix - = G, the eigenvector is 4 4 2 3 (A) 3 =2G (B) 4 =3G (C) 2 =-1G (D) - = G 1 2
  • 14. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Q. 78 Let, 0 1 . A 2 0 - = G and A = 3 1 2 1 a 0 b - = = G. Then (a + b) = (A) 7/20 (B) 3/20 (C) 19/60 (D) 11/20 2 # c m is Q. 79 The value of the integral I = 1 3 exp - x dx 2 8 p 0 (A) 1 (B) p (C) 2 (D) 2p Q. 80 Given an orthogonal matrix A R 1 1 1 0 1 1 1 0 1 1 0 1 1 1 0 1 SSSSS = - - - T V WWWWW X 6AAT @-1 is 1 SSSSSS WWWWWW SSSSSS WWWWWW 0 (A) 0 in 0 co.nodia.www.© 0 1 0 0 0 0 0 0 0 0 4 4 2 1 2 1 R T V X (B) 0 0 0 0 0 0 0 0 0 0 0 0 2 1 2 1 2 1 2 1 R T V X (C) 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 R SSSSS T V WWWWW X (D) 1 SSSSSS 0 0 0 0 1 0 0 0 0 1 0 0 0 0 4 4 4 1 4 R T V WWWWWW X ***********
  • 15. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS SOLUTIONS Sol. 1 Option (B) is correct. Here, as we know Limsin 0 q q" . 0 but for 10% error, we can check option (B) first, = = p = q 18 18 . c c# 0 314 180 c sinq = sin18c = 0.309 % error = 0 . 314 - 0 . 309 0 . 309 #100 % = 0 . 49 % Now, we check it for q = 50c in q = 50 c = 50 c# p = 0 . 873 180 co.c sinq nodia.= sin50c = 0.77 % error = 0.77 - 0.873 0 . 873 =- 12 . 25 % www.© so, the error is more than 10%. Hence, for error less than 10%, q = 18c can have the approximation sin q . q Sol. 2 Option (A) is correct. For, a given matrix A 6 @ the eigen value is calculated as A - lI = 0 where l gives the eigen values of matrix. Here, the minimum eigen value among the given options is l = 0 We check the characteristic equation of matrix for this eigen value A - lI = A (for l = 0) 3 5 2 5 12 7 2 7 5 = = 3^60 - 49h- 5^25 - 14h+ 2^35 - 24h = 33 - 55 + 22 = 0 Hence, it satisfied the characteristic equation and so, the minimum eigen value is l = 0 Sol. 3 Option (D) is correct. Given, the polynomial f^xh a4x 4 a x 3 a x 2 3 2 a x a = + + + 1 - 0 Since, all the coefficients are positive so, the roots of equation is given by f^xh = 0 It will have at least one pole in right hand plane as there will be least one sign change from ^a1h to ^a0h in the Routh matrix 1st column. Also, there will be a
  • 16. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS corresponding pole in left hand plane i.e.; at least one positive root (in R.H.P) and at least one negative root (in L.H.P) Rest of the roots will be either on imaginary axis or in L.H.P Sol. 4 Option (B) is correct. Consider the given matrix be Im + AB R 2 1 1 1 1 2 1 1 1 1 2 1 V 1 1 1 2 = SSSSS S T WWWWW W X where m = 4 so, we obtain AB R 2 1 1 1 1 2 1 1 1 1 2 1 V 1 1 1 2 R 1 0 0 0 0 1 0 0 0 0 1 0 V 0 0 0 1 SSSSS WWWWW = - S T SSSSS S T W X WWWWW W X 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 SSSSS WWWWW = co.in nodia.www.© R S T V W X 1 1 1 1 = R SSSSS S T V WWWWW W X 61 1 1 1@ Hence, we get A 1 1 1 1 = R SSSSS S T V WWWWW W X , B = 81 1 1 1B R Therefore, BA = 81 1 1 1B 1 SSSSS WWWWW 1 1 1 S T V W X = 4 From the given property Det ^Im + ABh = Det^Im + BAh & Det 2 1 1 1 1 2 1 1 1 1 2 1 1 1 1 2 R SSSSS S T V WWWWW W X Det R 1 0 0 0 0 1 0 0 0 0 1 0 0 0 0 1 SSSSS WWWWW ]] ]] = + 4 S T V W X Z [ _ bb bb ` a = 1 + 4 = 5 Note : Determinant of identity matrix is always 1. Sol. 5 Option (D) is correct. dx + x = t t dt
  • 17. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS dx dt t x + = 1 dx + Px = Q (General form) dt 1dt = # = # = = Integrating factor, IF e Pdt e t elnt t Solution has the form, x#IF = # ^Q#IFhdt + C x#t = # (1) (t)dt + C 2 xt = t2 + C Taking the initial condition, x(1) = 0.5 t2 0.5 = 1 2 co.+ C & in C = 0 t 2 So, nodia.xt = & 2 x = www.© Sol. 6 Option (C) is correct. 1 f (z) z 1 z 3 = 2 + - + 1 C p # = sum of the residues of the poles which lie 2 j f (z)dz inside the given closed region. C & z + 1 = 1 Only pole z =- 1 inside the circle, so residue at z =- 1 is. f (z) - + z 1 3 = 1 + + (z ) (z ) z z 1 1 ( )( ) = + + ( )( ) lim z z 1 3 2 2 1 z 1 + - + = = "- 1 C p # = 1 So 2 j f (z)dz Sol. 7 Option (A) is correct. = p + p x = -1 = i cos 2 i sin 2 So, x = ei 2p = 2p ^ h & ei i xx ei x ^ h = e 2-p 2 p Sol. 8 Option (D) is correct. d y t dy t ( ) ( ) ( ) dt dt y t 2 2 2 + + = d(t) By taking Laplace transform with initial conditions 0 dy 2 sy s y 0 Y s - - + - + ; E = 1 s Y(s) sy( ) dt [ ( ) ( )] ( ) t 2 0 = & 6s2Y(s) + 2s - 0@+ 26sY(s) + 2@+ Y(s) = 1 Y(s) [s2+ 2s + 1] = 1 - 2s - 4 Y(s) - - s 2 1 2 3 2 = + + s s We know that, If, y(t) Y(s) L
  • 18. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS then, dy t ( ) dt sY(s) y(0) L - So, sY(s) - y(0) - - + s s 2 1 2 3 ( ) s s 2 2 = + + ( ) 2 2 - s - s + s + s + 2 3 2 4 2 2 + + (s 2 s 1 ) = sY(s) - y(0) s s + 2 = + 1 + 1 2 2 2 = + + + (s 1 ) ( s 1 ) ( s 1 ) 1 1 2 = + + s 1 (s + 1 ) Taking inverse Laplace transform dy t ( ) dt = e-tu(t) + te-tu(t) dy At t = 0+, dt t=0+ = e0+ 0 = 1 Sol. 9 Option (A) is correct. Divergence of A in spherical coordinates is given as 1 1 in r A krn 2 co.r 2 nodia.www.© = 2 ( ) d:A ( ) r r 2 2 = 2 + r r 2 2 k n 2 rn 2 = ( + ) +1 r = k(n + 2)rn-1 = 0 (given) n + 2 = 0 & n =- 2 Sol. 10 Option (C) is correct. Probability of appearing a head is 1/2. If the number of required tosses is odd, we have following sequence of events. H, TTH, TTTTH, ........... 1 1 3 1 5 = +b l +b l + Probability P 2 2 2 ..... P 2 1 1 1 3 4 2 = - = Sol. 11 Option (B) is correct. f (x) = x3- 9x2+ 24x + 5 ( ) dx df x = 3x2- 18x + 24 = 0 & df x ( ) dx = x2- 6x + 8 = 0 x = 4, x = 2 d f x ( ) dx 2 2 = 6x - 18 For x = 2, d f x ( ) dx 12 18 6 < 0 2 2 = - =- So at x = 2, f (x) will be maximum f (x) max = (2)3- 9(2)2+ 24(2) + 5 = 8 - 36 + 48 + 5 = 25
  • 19. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 12 Option (B) is correct. Characteristic equation. A- lI = 0 5 2 - - - l 3 - = 0 l 5l + l2+ 6 = 0 l2+ 5l + 6 = 0 Since characteristic equation satisfies its own matrix, so A2+ 5A+ 6 = 0 & A2 =- 5A- 6I Multiplying with A A3+ 5A2+ 6A = 0 A3+ 5(- 5A- 6I) + 6A = 0 A3 = 19A+ 30I co.in nodia.www.© Sol. 13 Option (D) is correct. From Divergence theorem, we have ###4v $ Avdv A n ds = # v $ t s The position vector rv = ^utx x + utyy + utz zh Here, Av = 5rv, thus = ct + t + t 2 m ^t + t + t h 4$ Av u 2 x y z ux x uyy uz z : 2 x u y u z 2 2 2 = c dx + + dz m = 3#5 = 15 dy dx dy dz 5 ## v $ t = ### 15dv = 15V So, 5r nds s Sol. 14 Option (C) is correct. dy = ky We have dx # dy = # k dx + A Integrating y or lny = kx + A Since y(0) = c thus lnc = A So, we get, lny = kx + lnc or lny = lnekx + lnc or y = cekx Sol. 15 Option (A) is correct. C R Integrals is # - + where C is circle z = 1 z dz 4 5 3 4 z z C 2+ + f (z)dz C # = 0 if poles are outside C. Now z 2+ 4z + 5 = 0 (z + 2)2+ 1 = 0 Thus z1,2 2 j z1,2 > 1 =- ! & So poles are outside the unit circle.
  • 20. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 16 Option (C) is correct. We have f (x) = x + x - 3 = 0 fl(x) x = 1 + 1 2 Substituting x0 = 2 we get fl(x0) = 1.35355 and f (x0) = 2 + 2 - 3 = 0.414 Newton Raphson Method x1 f x ( ) = - 0 f x ( ) x 0 0 l Substituting all values we have = - 0 414 = 1.694 2 . 1 3535 x 1 . Sol. 17 Option (B) is correct. Writing A:B we have : : : 1 1 1 1 4 4 1 6 6 20 SSSS WWWW l m co.in nodia.www.© R T V X Apply R3 R3 R2 " - : : : 20 1 1 0 1 4 0 1 6 6 6 20 l - m - R SSSS T V WWWW X For equation to have solution, rank of A and A:B must be same. Thus for no solution; l = 6, m ! 20 Sol. 18 Option (C) is correct. Total outcome are 36 out of which favorable outcomes are : (1, 2), (1, 3), (1, 4), (1, 5), (1, 6), (2, 3), (2, 4), (2, 5), (2, 6); (3, 4), (3, 5), (3, 6), (4, 5), (4, 6), (5, 6) which are 15. Thus P(E) . = No of favourable outcomes = = 5 . No of total outcomes 15 36 12 Sol. 19 Option (C) is correct. Eigen value of a Skew-symmetric matrix are either zero or pure imaginary in conjugate pairs. Sol. 20 Option (C) is correct. For a function x(t) trigonometric fourier series is 3 = / = + w + w x(t) Ao [An cosn t Bn sinn t] n 1 Where, Ao T1 x(t)dt = # T0" fundamental period 0T 0 An = T2 # x(t)cosn w t dt 0T 0 Bn = T2 # x(t) sinn w t dt 0T 0 For an even function x(t),Bn = 0 Since given function is even function so coefficient Bn = 0, only cosine and constant
  • 21. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS terms are present in its fourier series representation. Constant term : 3 T 4 A0 = T1 x(t)dt 4 - # T / / T1 T Adt 2Adt = / + 3 4 - -: # # D T / T / T / 4 4 4 1 TA AT = : 2 - 2 2 D A2 T =- Constant term is negative. Sol. 21 Option (D) is correct. Given differential equation 2 d n x n x ( ) ( ) dx 2 - = 0 L 2 Let n(x) = Aelx l x in So, A l 2 e l x - Ae = 0 L 2 l 2 - 1 = l =!co.0 & L1 L 2 Boundary condition, nodia.n ( 3 ) = 0 so take l =- n ( x ) = Ae - n(0) = Ae0 = K & A = K So, www.n(x) = Ke-(x/L) L x L © 1 Sol. 22 Option (A) is correct. 1 = Given that ey x x 1 = or ln ey ln x x or y = x1 lnx Now dx dy ln x x x x 1 1 = + ^- - 1 ln x 2h 1 2 2 = - x x For maxima and minima : dy (1 ln ) 0 dx 1 x 2 = - = x lnx = 1 " x = e 1 Now d y dx 2 2 =- 2 - ln x x 3 b- 2 l- 1 1 x 3 x 2 b x l =- 2 + 2 ln - 1 2 3 3 x x x x d x dy atx e 2 2 = 1 2 2 1 < 0 2 3 3 = - + - e e e So, y has a maximum at x = e1 Sol. 23 Option (D) is correct. According to given condition head should comes 3 times or 4 times 4 1 1 P(Heads comes 3 times or 4 times) C 2 C 1 2 2 4 4 4 3 3 = b l + b l b l 1 16 = : + : : = 5 1 4 1 8 1 2 16
  • 22. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 24 Option (C) is correct. A v = t + 2 t dvl = dxatx + dyaty xyax x ay # A v : dl v (xyax x ay) (dxa dya ) C = # t + 2 t : t + t C x y = # + 2 (xydx x dy) C xdx xdx dy dy 3 3 4 3 = # 2 3 + # 1 3 + # + # = 1 : - D+ : - D+ - + 1 1 - 3 = 1 3 4 1 3 3 - = 1 2 - - © www.nodia.co.in 1 / / / / 2 3 1 3 3 1 1 3 2 3 2 [ ] [ ] 1 3 4 3 4 3 1 3 Sol. 25 Option (C) is correct. Given function X(z) z ( z z z 1 ) ( 2 ) Poles are located at z = 0, z = 1, and z = 2 At Z = 0 residues is = : R0 z Z zX ( ) = 0 - 2 = 1 2#0 - - (0 1) (0 2) = 1 Z at z = 1 , R1 = ( Z - 1) : X ( ) Z= 1 - = = 1 2#1 1 - 1(1 2) At z = 2, R2 (z 2) X(z) z 2 = - : = = 1 2 # 2 3 - 2(2 1) 2 - =- Sol. 26 Option (B) is correct. Taking step size h = 0.1, y(0) = 0 x y dy = x + y y y hdx dx dy i+1 = i + 0 0 0 y1 = 0 + 0.1(0) = 0 0.1 0 0.1 y2 = 0 + 0.1(0.1) = 0.01 0.2 0.01 0.21 y3 = 0.01 + 0.21#0.1 = 0.031 0.3 0.031 From table, at x = 0.3,y(x = 0.3) = 0.031 Sol. 27 Option (D) is correct. Given that f (t) - s + ; E L 1 3 1 3 2 = + + - s 4 s (K 3 )s limf (t) t"3 = 1 By final value theorem limf (t) t"3 = = limsF(s) 1 s " 0 or : + s ( 3 s 1 ) 4 3 + + - ( ) lim s 0 3 2 s s K s " = 1
  • 23. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS or + s ( 3 s 1 ) 4 3 s 0 s s 2+ s + K - [ ( )] lim " = 1 1- K 3 = 1 or K = 4 Sol. 28 Option (B) is correct. The highest derivative terms present in DE is of 2nd order. Sol. 29 Option (C) is correct. Number of elements in sample space is 210. Only one element "H,H,T,T,T,T,T,T,T,T, is event. Thus probability is 1 10 2 Sol. 30 Option (C) is correct. We have f (z) = c0 + c1z -1 in 1 + f ( z ) - 1 f1(z) = = 1 + co.c0 + c1z z z nodia.www.© = z ( 1 + c 0 ) + c 1 z 2 Since f1(z) has double pole at z = 0, the residue at z = 0 is Res f1(z)z=0 limz .f (z) z 0 2 = 1 " = + 0 + 1 . c m = c1 " z ( 1 c ) c lim z z z 0 2 2 Hence f1(z)dz # unit circle = # [ 1 + f ()] z dz = 2pj [Residue at z = 0] z unit circle = 2pjc1 Sol. 31 Option (D) is correct. We have f (x) sin x x p = - Substituting x - p = y ,we get f (y + p) = sin( y + p ) =- sin y (sin ) y y = -1 y y 3 5 1 y y y = - c - + - m ! ! ... y 3 5 or f (y + p) 2 4 1 y y ... =- + - + 3 5 ! ! Substituting x - p = y we get f (x) =- + ( - p ) 2 - - p 4 + ! ( ) ! ... x x 1 3 5 Sol. 32 Option (A) is correct. (A) dy dx = y x or # dy y = # dx x or log y = log x + log c or y = cx Straight Line Thus option (A) and (C) may be correct. (B) dy dx =-y x
  • 24. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS or # dy y =- # dx x or log y =- log x + log c or log y = log 1 + log c x or y x c = Hyperbola Sol. 33 Option (D) is correct. Sum of the principal diagonal element of matrix is equal to the sum of Eigen values. Sum of the diagonal element is -1 - 1 + 3 = 1.In only option (D), the sum of Eigen values is 1. Sol. 34 Option (C) is correct. The product of Eigen value is equal to the determinant of the matrix. Since one of the Eigen value is zero, the product of Eigen value is zero, thus determinant of the matrix is zero. Thus p11p22- p12p21 = 0 © www.nodia.co.in Sol. 35 Option (B) is correct. The given system is x y 4 2 2 = 1G= G 7 = =6G We have A 4 2 2 = = 1G and A 4 2 2 = 1 = 0 Rank of matrix r(A) < 2 Now C 4 2 2 1 7 = = 6G Rank of matrix r(C) = 2 Since r(A) ! r(C) there is no solution. Sol. 36 Option (A) is correct. sinz can have value between -1 to +1. Thus no solution. Sol. 37 Option (A) is correct. We have f (x) = ex + e-x For x > 0, ex > 1 and 0 < e-x < 1 For x < 0, 0 < ex < 1 and e-x > 1 Thus f (x) have minimum values at x = 0 and that is e0+ e-0 = 2. Sol. 38 Option (A) is correct. sin x 3 5 x x x ... = + + + 3 5 ! ! cos x 2 4 1 x x ... = + + + 2 4 ! ! Thus only sin(x3) will have odd power of x . Sol. 39 Option (B) is correct. We have dx t ( ) ( ) dt + 3x t = 0 or (D + 3)x(t) = 0 Since m =- 3, x(t) = Ce-3t Thus only (B) may be solution.
  • 25. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 40 Option (C) is correct. We have x = e-x or f (x) = x - e-x f'(x) = 1 + e-x The Newton-Raphson iterative formula is xn+1 f x ( ) = - n f x '( ) x n n x= - - n Now f (xn) xn e f'(xn) 1 e x= + - n x - - x e 1 n x n = - Thus xn+1 x e n n + - x e 1 + ( ) n e 1 x x n n = + - - Sol. 41 Option (A) is correct. 1 d n - 1 Res f (z)( z in a ) n z=a ( n 1 )! co.f () z dz n nodia.www.© 1 z a = - - - = 6 @ Here we have n = 2 and a = 2 Thus Res f (z)z=2 1 2 ( )! d z ( ) 1 ; E dz ( ) ( ) 2 1 z z 2 2 z a 2 2 2 = - - - + = d 1 ; E dz ( z 2 ) z a 2 = + = 2 - (z 2) z a 3 = + = ; E =- 2 32 64 =- 1 Sol. 42 Option (D) is correct. eP = L-1 (sI -A)-1 6 @ - L s 0 s 0 0 2 1 3 1 1 = - - - - e= G = Go L s 2 s 1 3 1 1 = - + - - e= G o s 3 + L ( )( ) 2 - ( )( ) 1 ( )( ) ( )( ) s s s s s s s s s 1 1 2 1 2 1 2 1 2 = - + + + + + + + + f> Hp 1 - 2 1 2 e e e e 1 2 e e e e 2 2 2 2 = 1 2 - + - - + - - - - - - = - - G Sol. 43 Option (B) is correct. Taylor series is given as x a f a x a f a "( ) ... f (x) ( ) ! '( ) ( ) ! f a 1 2 2 = + - + - + For x = p we have Thus f (x) ( ) f x f "( )... ! '( ) ( ) ! x f x 1 2 2 = p + - p p + - p Now f (x) = ex + sinx f'(x) = ex + cos x f"(x) = ex - sinx f"(p) = ep - sinp = ep
  • 26. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Thus the coefficient of (x - p)2 is p f"( ) 2 ! Sol. 44 Option (A) is correct. The equation of straight line from (0,0) to (1,2) is y = 2x . Now g(x,y) = 4x3+ 10y4 or, g(x,2x) = 4x3+ 160x4 1 Now g(x,2x) 1 # (4x3 160x4)dx 0 = # + 0 = [x4 + 32x5] 1 = 33 0 Sol. 45 Option (B) is correct. Q = # + 2 xdx 2 ydy I 2 (xdx ydy) P Q = # + # P 2 xdx 2 ydy 0 Q P = # + # = 0 1 1 0 © www.nodia.co.in Sol. 46 Option (B) is correct. The given plot is straight line whose equation is x y -1 1 + = 1 or y = x + 1 Now I ydx 1 2 = # (x 1)dx 1 2 = # + (x ) 2 1 2 2 = + ; E . = 9 - 4 = 2 5 2 2 Sol. 47 Option (C) is correct. coth x = cosh x sinh x as x << 1, coshx . 1 and sinhx . x Thus coth x . 1 x Sol. 48 Option (A) is correct. sin 0 lim ^ q h 2 q" q q ^ sin 0 2 2 ^ h = lim 2 q" q h = lim 2 sin 1 2 q" q 0 2 q ^ ^ h h = 1 = 0 . 5 2 Sol. 49 Option (D) is correct. We have, lim 1 x"0 2 x = 3 lim x x 2 "3 = 3 lim e x x "3 - = 3 lim e x x2 "3 - = 0 lim e x x 0 2 " - = 1 Thus e x- 2 is strictly bounded. Sol. 50 Option (A) is correct. We have f (x) = e-x = e-(x - 2) - 2 = e-(x - 2)e-2 x ... ( ) ( ) ! x 1 2 e 2 2 2 = - - + - -2 ; E
  • 27. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS = 1 - (x - 2) e-2 6 @ Neglecting higher powers = (3 - x)e-2 Sol. 51 Option (D) is correct. We have k 2 2 d y dx 2 = y - y2 or 2 d y dx y 2 - k 2 y 2 =- 2 k A.E. D 2 1 2 - = 0 k or D =!1 k C.F. = C1e - x x k + C2e k P.I. = 1 - y 2 2 c 2 m = in y D - 1 k 2 2 k 2 Thus solution is co.y = C1e - x x k + C2e k + y2 From y(0) = y1 we get C1+ nodia.C2 = y1- y2 From y(3) = y2 we get that C1 must be zero. Thus www.C2 = y1- y2 y = (y1 - y2)e - x k + y2 © Sol. 52 Option (B) is correct. We have f (x) = x3- x2+ 4x - 4 f'(x) = 3x2- 2x + 4 Taking x0 = 2 in Newton-Raphosn method x1 f x ( ) = - 0 '( ) x f x 0 0 3 2 - + - 2 2 42 4 ( ) 2 ( ) ( ) 2 3 2 2 2 4 = - - + 3 4 = Sol. 53 Option (C) is correct. For two orthogonal signal f (x) and g(x) # + f (x)g(x)dx = 0 3 3 - i.e. common area between f (x) and g(x) is zero. Sol. 54 Option (A) is correct. We know that # 1 ds = 2pj [sum of residues] s 2 - 1 D Singular points are at s =!1 but only s =+ 1 lies inside the given contour, Thus Residue at s =+ 1 is - lim(s 1) f (s) s " 1 lim(s ) s 1 1 1 1 2 s 1 2 = - - = " # 1 ds 2 j j s 2 - 1 D = p ` 1 j = p 2
  • 28. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 55 Option (C) is correct. For two orthogonal vectors, we require two dimensions to define them and similarly for three orthogonal vector we require three dimensions to define them. 2M vectors are basically M orthogonal vector and we require M dimensions to define them. Sol. 56 Option (A) is correct. We have f (x) = x2- x + 2 f'(x) = 2x - 1 = 0 x " = 1 2 f"(x) = 2 Since f"(x) = 2 > 0, thus x = 1 is minimum point. The maximum value in 2 closed interval 6-4,4@ will be at x =- 4 or x = 4 Now maximum value = max[f (- 4), f (4)] = max(18,10) = 18 © www.nodia.co.in Sol. 57 Option (C) is correct. Probability of failing in paper 1 is P(A) = 0.3 Possibility of failing in Paper 2 is P(B) = 0.2 Probability of failing in paper 1, when student has failed in paper 2 is P 0.6 B ^A h = We know that A b l P B P + B = ( ) P B ( ) = bAl = 0.6 # 0.2 = 0.12 or P(A + B) P(B)P B Sol. 58 Option (C) is correct. We have A R 1 1 1 1 1 1 1 0 1 SSSS V 1 1 0 1 1 0 1 0 0 SSSS WWWW = - + - T R T X V WWWW X R3- R1 Since one full row is zero, r(A) < 3 Now 1 1 1 -1 =- 2 ! 0, thus r(A) = 2 Sol. 59 Option (D) is correct. The vector Triple Product is A# (B #C) = B(A$ C) -C(A$ B) Thus 4#4#P =4 (4$ P) - P(4$4) =4 (4$ P) -42P Sol. 60 Option (A) is correct. The Stokes theorem is ## (4# F) $ ds = # A $ dl Sol. 61 Option (C) is correct.
  • 29. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS 3 -# = 1 We know p(x)dx 3 3 -a -# = 1 Thus Ke x dx 3 0 # a + # 3 -a = 1 - or Ke x dx Ke x dx 0 3 or K e x 0 k e x a a 0 3+ - 6 a @ 6 - a @ 3 = 1 ( ) - or K K a + a = 1 or K 2 a = Sol. 62 Option (A) is correct. We have xo (t) + 2x(t) = s(t) Taking Laplace transform both sides sX(s) - x(0) + 2X(s) = 1 co.in nodia.www.© or sX(s) + 2X(s) = 1 Since x(0-) = 0 X(s) = 1 + s 2 Now taking inverse Laplace transform we have x(t) = e-2tu(t) Sol. 63 Option (A) is correct. Sum of the Eigen values must be equal to the sum of element of principal diagonal of matrix. Only matrix 6 2 2 = 6G satisfy this condition. Sol. 64 Option (B) is correct. We have W = lnz u + jv = ln(x + jy) or eu+jv = x + jy or eu ejv = x + jy eu (cos v + j sinv) = x + jy Now x = eu cos v and y = eu sinv Thus x2+ y2 = e2u Equation of circle Sol. 65 Option (D) is correct. We have z dz 4 1 z j 2 # 2 + - = 1 (z i) (z i) dz 2 2 # z j 2 = + - - = P(0,2) lies inside the circle z - j = 2 and P(0, - 2) does not lie. Thus By cauchy’s integral formula = p - I ( ) 1 " + - ( )( ) i lim z i z i z i 2 2 2 2 z 2i = p p # 2 i = i i 2 2 2 C + Sol. 66 Option (C) is correct. = q q p # I sin3 d 0
  • 30. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS = # p ` 3 sin q - sin 3 q j d q sin3q = 3 sinq - 4 sin3q 4 0 = - q = w q p p 3 s 4 cos 3 : D : D 12 0 0 4 3 4 3 1 12 1 12 y a k P y+d = ( ) P d = 0 006 = 0 4 . . 0 015 © www.nodia.co.in 3 4 = 8 + B-8 + B= Sol. 67 Option (D) is correct. Let d " defective and y " supply by Y p d ( ) P(y + d) = 0.3 # 0.02 = 0.006 P(d) = 0.6 # 0.1 + 0.3 # 0.02 + 0.1 # 0.03 = 0.015 P d y a k . Sol. 68 Option (C) is correct. We have A 4 2 2 = = 4G Now 6A - lI @[X] = 0 or - = - G= G 4 2 2 4 101 101 l l 0 = =0G or (101)(4 - l) + 2(101) = 0 or l = 6 Sol. 69 Option (A) is correct. We have 2 d y k y 2 dx + 2 = 0 or D2y + k2y = 0 The AE is m2+ k2 = 0 The solution of AE is m =!ik Thus y = Asinkx + Bcos kx From x = 0, y = 0 we get B = 0 and x = a,y = 0 we get Asinka = 0 or sinka = 0 k = mpx a =/ ` p j Thus y A sin m x a m m Sol. 70 Option (A) is correct. We have f (x) e 1 e x x = + For x " 3, the value of f (x) monotonically increases. Sol. 71 Option (B) is correct. Order is the highest derivative term present in the equation and degree is the power of highest derivative term. Order = 2, degree = 1 Sol. 72 Option (D) is correct. Probability of coming odd number is 2 1 and the probability of coming even number is 2 1 . Both the events are independent to each other, thus probability of coming
  • 31. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS odd number after an even number is 2 1 # = 1 . 2 1 4 Sol. 73 Option (B) is correct. We have 2 d y dx 5 dy 6y 2 - + = 0 dx The A.E. is m2- 5m + 6 = 0 m = 3,2 The CF is yc = C 3 x 2 x 1 e + C 2 e Since Q = 0, thus y = C e x + C e 2 x 1 3 2 Thus only (B) may be correct. Sol. 74 Option (A) is correct. We have f (t) = e(a+2)t+5 = e5.e(a+2)t Taking Laplace transform we get F(s) = 5 1 co.in nodia.www.© ; - + E Thus Re(s) > (a + 2) ( ) e s a 2 Sol. 75 Option (C) is correct. For x > 0 the slope of given curve is negative. Only (C) satisfy this condition. Sol. 76 Option (C) is correct. Newton - Raphson " Method-Solving nonlinear eq. Runge - kutta Method " Solving ordinary differential eq. Simpson’s Rule " Numerical Integration Gauss elimination " Solving linear simultaneous eq. Sol. 77 Option (C) is correct. We have A - = G 4 4 2 = 3 Characteristic equation is A - lI = 0 or 4 4 2 3 l l - - = 0 or (- 4 - l)(3 - l) - 8 = 0 or -12 + l + l2- 8 = 0 or l2+ l - 20 = 0 or l =- 5,4 Eigen values Eigen vector for l =- 5 - l = 0 ( ) A I Xi 1 - ( - 5 ) 2 x = 4 8 - 4 G= x G 1 2 0 = =0G x x 1 0 2 0 1 2 = =G G 0 = =0G R2- 4R1 x1+ 2x2 = 0 Let -x1 = 2 & x2 =- 1, Thus X 2 = =-1G Eigen vector
  • 32. GATE SOLVED PAPER - EC ENGINEERING MATHEMATICS Sol. 78 Option (A) is correct. We have A - 2 . 0 0 1 = G and A = 3 1 2 1 a 0 b - = = G Now AA-1 = I or 0 1 3 0 2 1 . a = =G G b 2 0 - 1 0 0 = = 1G or - a . b 2 01 = G b 1 0 3 1 0 0 = = 1G or 2a - 0.1 = 0 and 3b = 1 Thus solving above we have b = 1 and a 3 = 1 60 Therefore a + b = 1 + = 7 3 1 60 20 Sol. 79 Option (A) is correct. Gaussian PDF is 1 (x co.) in nodia.www.© -m # for -3 # x # 3 3 - - f (x) e dx 2 2 2 2 p s = 3 s 3 -# = 1 and f (x)dx 3 Substituting m = 0 and s = 2 in above we get 1 x -# 3 - 2 e dx = 1 2 2 8 p 3 1 2 or 2 e dx 2 2 0 x 8 p # 3 - = 1 1 2 or e dx 2 0 x 8 p # 3 - = 1 Sol. 80 Option (C) is correct. From orthogonal matrix [AAT] = I Since the inverse of I is I , thus [AAT]-1 = I-1 = I *********