Answer
$y=2 \cos 2x$
Work Step by Step
Upon inspection, we realize that the graph is a cosine function with an amplitude of 2 and a period of $\pi$.
In the standard equation $y=a \cos bx$, $a$ is the amplitude. Since the amplitude is 2, a is equal to 2. To find the value of b, we use the formula:
Step 1: Period$=\frac{2\pi}{b}$
Step 2: $\pi=\frac{2\pi}{b}$
Step 3: $b=\frac{2\pi}{\pi}$
Step 4: $b=2$
Substituting the values of $a$ and $b$ in the equation $y=a \cos bx$, we find that the equation of the graph is $y=2 \cos 2x$.