2. • Trigonometry is derived from Greek words trigonon(three
angles) and metron (measure).
• Trigonometry is the branch of mathematics which deals
with triangles, particularly triangles in a plane where one
angle of the triangle is 900.
• Trigonometry specifically deals with relationships between the
sides and the angles of a triangle, i.e. on the trigonometric
functions, and with calculations based on these functions.
• The origins of trigonometry can be traced to the ci-
vilizations of ancient Egypt, Mesopotamia and the
Indus Valley, more than 4000 years ago.
• Some experts believe that trigonometry
was originally invented to calculate
• The first recorded use of trigonometry
came from the Hellinistic mathematician
Circa in 150 BC.
• Many mathemiticians like Aryabhatta, Ibn Yunus
and Al-Kashi also contributed significantly.
5. Right Triangle
• A triangle in which one angle is
equal to 900
is called a right angled
• The side opposite to the right angle
is known as hypotenuse.
AC is the hypotenuse
• The other two sides are known as
legs or base and altitude
AB and AC are base and altitude
6. Pythagoras Theorem
• In any right triangle, the area of the square
whose side is the hypotenuse is equal to the
sum of the areas of the squares whose sides are
the two legs.
• In the figure,
7. Trigonometric Ratios
Sine (sin) Opposite side / Hypotenuse
Cosine (cos) Adjacent side / Hypotenuse
Tangent (tan) Opposite side / Adjacent side
Cosecant (cosec) Hypotenuse / Opposite side
Secant (sec) Hypotenuse / Adjacent side
Cotangent (cot) Adjacent side / Opposite side
8. Value for Trigonometric Functions for Angle C
• Sinθ = AB/AC
• Cosθ = BC/AC
• Tanθ = AB/BC
• Cosecθ = AC/AB
• Secθ = AC/BC
• Cotθ = AC/AB
11. Some Applications of Trigonometry
• Main use is in Construction or else this field of mathematics
can be applied in astronomy,navigation, acoustics medical
imaging, civil engineering, seismology, electrical
engineering phonetics, chemistry, number theory and many