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1983 AHSME Problems/Problem 11

Revision as of 18:46, 26 January 2019 by Sevenoptimus (talk | contribs) (Replaced the solution with one that's actually correct)

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

By the addition formula for $\sin$, this becomes $\sin{((x-y)+y)} = \sin{x}$, so the answer is $\fbox{B}$.

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