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

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