(adsbygoogle = window.adsbygoogle || []).push({}); 1. The problem statement, all variables and given/known data

Find all possible solutions:

2cos^{2}2θ = 1 - cos2θ

3. The attempt at a solution

I know all my arithmetic is correct, but when it comes to giving the answer, I'm not sure how to write it.

2cos^{2}2θ + cos2θ - 1 = 0

(2cos2θ - 1)(cos2θ + 1) = 0

2cos2θ = 1

cos2θ = 1/2

2θ = ∏/3

cos2θ = -1

2θ = ∏

So θ is equal to ∏/6 and ∏/2

But the solutions are supposed to be:

∏/6 + ∏n

5∏/6 + ∏n

∏/2 + ∏n

And I don't understand why. Can someone explain it to me please?

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# Homework Help: Help Understanding Trig Equation

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