4. Introduction of another formula for
area of a triangle
• Most of us are aware with :
• Area of a triangle =
Where b = base and h = corresponding height
of the triangle
5. Examples :
• 1) Find the area of a triangle having sides :
AB = 4 cm
BC = 3 cm
CD = 5 cm
8. Example 2:
2) Rahul has a garden, which is triangular in
shape. The sides of the garden are 13 m, 14 m,
and 15 m respectively. He wants to spread
fertilizer in the garden and the total cost
required for doing it is Rs 10 per m2
. He is
wondering how much money will be required to
spread the fertilizer in the garden
9. Solution of Example 2)
• Given a = 13 m , b = 14 m and c = 15 m
So , we will find
the area of the
triangle by
using Heron’s
formula.
11. Continue …
• Given the rate = Rs 10 per m^2
• Now :
• Total cost = Rs. 10 * 84 = Rs 840/-
12. Area of a quadrilateral
• Suppose there is a quadrilateral
having sides : a , b , c and d and
diagonal r.
The diagonal d divides the quadrilateral into 2
triangles.
So : Ar(ABCD)= Ar(ABD) + Ar(BCD)
13. Continued
1) Area of triangle : ABD
Heron’s formula:
Putting the values we get :
16. Solution of example
As we have the formula written below for the
area of a quadrilateral
Where :
a = 4cm
b = 3 cm
c = 5 cm
d = 6 cm
And r (diagonal ) = 7 cm
