Answer
$\pi$
Work Step by Step
$\cos^2 x+2\cos x+1=0$
$(\cos x+1)^2=0$
$\cos x+1=0$
$\cos x=-1$
The only solution in $[0, 2\pi)$ is $\pi$.
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 - 7.6 Trigonometric Equations - 7.6 Exercises - Page 720: 23
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