Answer
C
Work Step by Step
$arccos(\frac{-\sqrt 2}{2})=x$
$cosx=-\frac{1}{\sqrt 2}$ or $cosx=cos45^{\circ}$
Thus, $x=45^{\circ}$or $\frac{3\pi}{4}$
which is equal to $\frac{3\pi}{4}$.
Hence, the correct option is C.
Trigonometry (10th Edition)
by Lial, Margaret L.; Hornsby, John; Schneider, David I.; Daniels, Callie
Published by
Pearson
ISBN 10:
0321671775
ISBN 13:
978-0-32167-177-6
Chapter 6 - Inverse Circular Functions and Trigonometric Equations - Section 6.4 Equations Involving Inverse Trigonometric Functions - 6.4 Exercises - Page 279: 3
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