Precalculus (6th Edition)

Published by Pearson
ISBN 10: 013421742X
ISBN 13: 978-0-13421-742-0

Chapter 7 - Trigonometric Identities and Equations - Chapter 7 Test Prep - Review Exercises: 79

Answer

$y=\displaystyle \frac{3\pi}{4}$

Work Step by Step

By definition of arccos, y is the number from $[0, \pi]$ such that $\displaystyle \cos y=-\frac{\sqrt{2}}{2}.$ Using the unit circle, $\displaystyle \cos\frac{3\pi}{4}=-\frac{\sqrt{2}}{2}$, and $\displaystyle \frac{3\pi}{4}\in[0, \pi] ,$ so $y=\displaystyle \frac{3\pi}{4}$
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