Final Cover - For Printing

TRIGONOMETRY

Trigonometry
Trigonometry is a branch of mathematics which deals with the relations between the
measurements of sides and the angles of a triangle. Hipparchus, a Greek astronomer and
mathematician developed trigonometry and used its principles in predicting the paths and
positions of the heavenly bodies. The word ‘trigonometry’ is derived from two Greek words
‘trigon’ which means triangle and ‘metra’ which means measurement.

1. Pythagoras theorem
   In a right angled triangle the area of the square constructed on the hypotenuse is
   equal to the sum of the areas of the squares constructed on the other two sides.

Let ABC be a right triangle in which the measure of angle ABC = 90^0. Then the side
opposite to the right angle, AC is called the hypotenuse of the right triangle. Note
that the hypotenuse is the longest side of a right triangle.

Therefore, according to the Pythagoras theorem,

AC^2 = AB^2 + BC^2

Module 81 : Trigonometry

A

B C

θ