Chapter 4 - Section 4.5 - Graphs of Sine and Cosine Functions - Exercise Set - Page 595: 22

Please see below.

Please note that a sine function $y=A\sin (Bx-C)$ has amplitude $|A|$, period $\frac{2\pi }{B}$, and phase shift $\frac{C}{B}$. So the function $y=3\sin (2x- \frac{\pi }{2})$ has amplitude $|3|=3$, period $\frac{2\pi }{2 }=\pi $, and phase shift $\frac{\frac{\pi }{2}}{2}=\frac{\pi }{4}$.