Question

Prove the following identities. cos(3pi/s+x)=sinx

Answer 1

$\cos \left(\frac{3\pi}{2}-x \right)=\sin x \\ \\ =\cos \left(\frac{3\pi}{2} \right)\cos x -\sin \left(\frac{3\pi}{2} \right) \sin x \\ \\ =0\cos x -(-1)(\sin x) \\ \\ =\sin x$