Answer
$Amplitude = 4$
$Period = \pi$
$Horizontal\ shift = \frac{\pi}{4}$ i.e right shift $\frac{\pi}{4}$
$Vertical\ shift = 0$ (No vertical shift)
Work Step by Step
If C is any real number and $B> 0$, then the graphs of $y = k + A\sin(Bx+C)$ and $y = k + A\cos (Bx+C)$ will have
$Amplitude = |A|$
$Period = \frac{2\pi}{B}$
$Horizontal\ shift = –\frac{C}{B}$
$Vertical\ shift = k$
so for $y = 4\cos (2x - \frac{\pi}{2} )$
$Amplitude = |4| = 4$
$Period = \frac{2\pi}{2} = \pi$
$Horizontal\ shift = (–\frac{–\frac{\pi}{2}}{2}) = \frac{\pi}{4}$ i.e right shift $\frac{\pi}{4}$
$Vertical\ shift = 0$ (No vertical shift)