Chapter 12 : Troigonometry

Trigonometry Identities

Let us take any acute angle taking point P on OB we draw perpendicular PQ on OAB. Thus we have a right angled triangle OPQ. If we suppose

We have OQ² + PQ² = OP²--------------(1)

Dividing both sides of (i) by OP² we get

Similarly, dividing both sides of (1) by OQ² we get

A gain dividing both sides of (i) by PQ² , we get

Here, (2), (3) and (4) are all identities. These can be used to express one trigonometric ratio to other trigonometric ratio. For example:

Similarly,