1983 AHSME Problems/Problem 11

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Problem 11

Simplify $\sin (x-y) \cos y + \cos (x-y) \sin y$.

$\textbf{(A)}\ 1\qquad \textbf{(B)}\ \sin x\qquad \textbf{(C)}\ \cos x\qquad \textbf{(D)}\ \sin x \cos 2y\qquad \textbf{(E)}\ \cos x\cos 2y$

Solution

Take $y=0\implies \sin(x)$, so $\fbox{B}$