#### 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 $\pi$.

Published by
Pearson

ISBN 10:
013421742X

ISBN 13:
978-0-13421-742-0

$\pi$

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