Question #fe77f

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Answer 1 · 2016-10-11T18:16:24

Start by simplifying the left side:

$sin^2theta = 16cos^4theta - 12cos^2theta + 1$

$1 - cos^2theta = 16cos^4theta - 12cos^2theta + 1$

$0 = 16cos^4theta - 11cos^2theta$

$0 = cos^2theta(16cos^2theta - 11)$

$theta = pi/2, (3pi)/2, cos^-1(+-sqrt(11)/4)$

Hopefully this helps!