CLASS-9
INTRODUCTION OF TRIGONOMETRICAL RATIOS

TRIGONOMETRICAL RATIOS -

Trigonometry – Trigonometry is a to some extend the part of mathematics which shows the way towards higher level of mathematics. It is branch or another portion of mathematics which deals with the measurement of the sides & and angles of a triangle.

Base, Perpendicular, and Hypotenuse of a Right Triangle

In △ABC, ∠B = 90⁰, then –

(i) For ∠A, we have –

Base = AB, Perpendicular = BC, and Hypotenuse = AC

(ii) For ∠C, we have –

Base = BC, Perpendicular = AB, and Hypotenuse = AC

So, in a right angled triangle, for a given angle,

a) The side opposite to the right angle is called hypotenuse

b) The side opposite to the given angle is called perpendicular

c) The third side (i.e. the side forming the given angle with the hypotenuse), is called base.