Answer
D
Work Step by Step
$\cos \left( \dfrac {\pi }{2}-x\right) =\cos \dfrac {\pi }{2}\cos x+\sin \dfrac {\pi }{2}\sin x=0\times \cos x+1\times \sin x=\sin x\Rightarrow 3\rightarrow D$
Precalculus (6th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
013421742X
ISBN 13:
978-0-13421-742-0
Chapter 7 - Trigonometric Identities and Equations - 7.3 Sum and Difference Identities - 7.3 Exercises - Page 678: 3
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