# Trig identity proof.

Prove:
$\frac{CosθSinθ}{1 + Tanθ}$ = Cos2θ
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I multiply out the denominator to get:

CosθSinθ = Cos2θ + CosθSinθ

I cannot seem to prove it.

Starting to think it's a trick question.. :/

You might be asked to solve the equation instead of proving the identity, and the solutions of the equation are the zeros of cosine, id est odd integer multiples of $\pi/2$.