Question

find - cos(3π/2+X)
(it's a part of another question)​

Answer 1

$\: \: \: \: \: cos( \frac{3\pi}{2} + x) \\ = cos \frac{3\pi}{2} cosx - sin \frac{3\pi}{2} sinx \\ = (0)(cosx) - ( - 1)sinx \\ = sinx$