Solved

Evaluate the Expression $\sin x \sin ( x + y ) + \cos x \cos ( x + y )$

Question 19

Multiple Choice

Evaluate the expression. $\sin x \sin ( x + y ) + \cos x \cos ( x + y )$

A) $\sin ^ { 2 } x - \sin ^ { 2 } y$
B) 0
C) $\sin x \cos x + \sin y \cos y$
D) $\cos y$
E) $\cos ^ { 2 } x - \sin ^ { 2 } x$

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