Chapter 4 - Graphs of the Circular Functions - Summary Exercises on Graphing Circular Functions - Page 181: 8

$y = 10~cos~(\frac{x}{4}+\frac{\pi}{2})$ We can see the graph below.

$y = 10~cos~(\frac{x}{4}+\frac{\pi}{2})$ When $x = 0$, then $y = 10~cos~\frac{\pi}{2}= 0$ When $x = 2\pi$, then $y = 10~cos~\pi = -10$ When $x = 4\pi$, then $y = 10~cos~\frac{3\pi}{2}= 0$ When $x = 6\pi$, then $y = 10~cos~2\pi = 10$ When $x = 8\pi$, then $y = 10~cos~\frac{5\pi}{2} = 0$ We can see the graph below.