sin(x/2)=cos(3x/2) - Math Central

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Question from Valentine, a student:

sin(x/2)=cos(3x/2)
I was trying to use cos3x=cos(2x+x) but there wasn't any progress

Hi Valentine,

Try using the identity that $\cos(y) = \sin\left(y + \frac{\pi}{2}\right)$ to rewrite the right side.

Penny

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