Answer
$0$
Work Step by Step
We need to compute $\cos (\dfrac{-3 \pi}{2})$.
The trigonometric function $\cos$ has a period of $2\pi$. Also, because cosine is even, $\cos (-x)=\cos (x)$
Thus, we can simplify as follows:
$\cos (\dfrac{-3 \pi}{2}) =\cos (\dfrac{3 \pi}{2}) \\ =0$
