1.

What is the value of cos(A + B) + cos (A – B) ? (A) 2 sin A cos B (B) 2 cos A sin B (C) 2 cos A cos B (D) 2 sin A sin B.

Answer»

The correct option is (C) 2 cos A cos B

Explanation:

cos (A + B) + cos (A – B)

 cosAcosB – sinAsinB + cosAcosB + sinAsinB 

 2cosAcosB



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