Answer
amplitude $\frac{1}{4}$, period $ 4\pi$, no vertical translation, and phase shift $\pi$ to the left.
Work Step by Step
Given $y=-\frac{1}{4}\ cos(\frac{1}{2}x+\frac{\pi}{2})=-\frac{1}{4}\ cos\frac{1}{2}(x+\pi)$, we can find the following: amplitude $\frac{1}{4}$, period $p=\frac{2\pi}{1/2}=4\pi$, no vertical translation, and phase shift $\pi$ to the left.
