University Calculus: Early Transcendentals (3rd Edition)

The period of the graph is $2$.
The given graph shows the function of $y=\cos{\pi{x}}$ As shown in the cosine graph, the period of the graph is: $2\pi$ The graph of $\cos{x}$ is compressed by $\pi$, so the new period is: $2\pi\div\pi=2$