Precalculus: Mathematics for Calculus, 7th Edition

Published by Brooks Cole
ISBN 10: 1305071751
ISBN 13: 978-1-30507-175-9

Chapter 7 - Section 7.2 - Addition and Subtraction Formulas - 7.2 Exercises - Page 551: 31

Answer

$\sin(\frac{\pi}{2}-x)=\sin(\frac{\pi}{2}+x)$

Work Step by Step

First, let's simplify the left side: $\sin(\frac{\pi}{2}-x)$ Expand using the subtraction formula for sine: $=\sin\frac{\pi}{2}\cos x-\cos\frac{\pi}{2}\sin x$ Evaluate $\sin\frac{\pi}{2}$ and $\cos\frac{\pi}{2}$: $=1*\cos x-0*\sin x$ $=\cos x$ Now let's simplify the right side: $\sin(\frac{\pi}{2}+x)$ Expand using the addition formula for sine: $=\sin\frac{\pi}{2}\cos x+\cos\frac{\pi}{2}\sin x$ Evaluate $\sin\frac{\pi}{2}$ and $\cos\frac{\pi}{2}$: $=1*\cos x+0*\sin x$ Simplify: $=\cos x$ Since both sides are equal to $\cos x$, the identity is proven.
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