Given $\sin y=-\frac{4}{5}, \cos x=\frac{1}{2}$ With $\frac{3 \pi}{2}<x<2 \pi$ And $\pi<y<\frac{3 \pi}{2}$ , Find the Exact Values for the Following:
-

Given $\sin y=-\frac{4}{5}, \cos x=\frac{1}{2}$ with $\frac{3 \pi}{2}<x<2 \pi$ and $\pi<y<\frac{3 \pi}{2}$ , find the exact values for the following:
- $\cos (x+y)$