Answer :


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°




Hence Proved


iii. We know, 2 sin A cos B = sin (A + B) + sin (A – B)





= sin 90° + sin 60°




Hence Proved


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