Prove that :
i.
ii.
iii.
i. We know, 2 sin A sin B = cos (A – B) – cos (A + B)
= cos 60° - cos 90°
Hence Proved
ii. We know, 2 cos A cos B = cos (A + B) + cos (A – B)
= cos 90° + cos 60°
iii. We know, 2 sin A cos B = sin (A + B) + sin (A – B)
= sin 90° + sin 60°