Prove that:
Take L.H.S
Multiplying & Dividing by 2:
{∵ 2 sin A sin B = cos (A – B) – cos (A + B)}
{∵ cos (-A) = cos A}
Multiplying & Dividing by 2:
{∵ 2 cos A sin B = sin (A + B) – sin (A – B)}
{∵ sin (-A) = - sin A}
{∵ sin (180° - A) = sin A}
= R.H.S
Hence Proved