Michael J. answered 04/09/17
Tutor
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Effective High School STEM Tutor & CUNY Math Peer Leader
Use trigonometric identities.
Let x=θ
2sinxcosx = 4(1 - 2sin2x)
sinxcosx = 2(1 - 2sin2x)
Get everything in terms of sine or cosine using the Pythagorean identity.
sinx√(1 - sin2x) = 2(1 - 2sin2x)
Square both sides of the equation.
sin2x(1 - sin2x) = 4(1 - 2sin2x)2
Can you finish from here?