# Chapter 4 - Test - Page 647: 15

See graph and explanations.

#### Work Step by Step

Step 1. From the given function $y=-2cos(x-\frac{\pi}{2})$, we can identify its amplitude as $A=2$, its period as $p=2\pi$, and there is a phase shift of $\frac{\pi}{2}$. Step 2. We can graph the function, using test points or transformation from $y=2cos(x)$ (shift right $\frac{\pi}{2}$ and reflect around the x-axis), for one period in $[0,2\pi]$ as shown in the figure.

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