Answer
$y=5cos(\frac{\pi}{4} x)$
Work Step by Step
1. Based on the given graph, we can initially identify that it resembles a graph of cosine.
2. We can determine the amplitude $|A|=5$, period $p=8$, passing $(0,5)$.
3. Write a model as $y=5cos(\omega x)$
4. We have $\frac{2\pi}{\omega}=8$, thus $\omega=\frac{\pi}{4}$
5. The equation is $y=5cos(\frac{\pi}{4} x)$
