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# Find all possiblie values of if ​

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Find all possiblie values of $$\cos(\theta)$$ if $$\cos(2\theta) = 2\cos(\theta) .$$

Oct 23, 2021

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I am pretty sure I saw this question answered yesterday.  Go see if you can find it.

Hint:

cos(2x)=cos^2x-sin^2x

and

sin^2x=1-cos^2x

simplify then sub   y=cos(theta)