How do you solve cos2x=cos^2xcos2x=cos2x from [-pi,pi][−π,π]?

1 Answer
Nghi N.
Jul 12, 2015

Solve cos 2x = cos^2 xcos2x=cos2x

Explanation:

Use trig identity: cos 2x = 2cos^2 x - 1cos2x=2cos2x−1

2cos^2 x - 1 = cos^2 x --> cos ^2 x = 1 --> cos x = + 1 -> x = 02cos2x−1=cos2x−→cos2x=1−→cosx=+1→x=0

Between interval (-pi, pi) -> x = 0 (−π,π)→x=0

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