Precalculus (6th Edition) Blitzer

The red graph is the graph of $y=4 \cos (2x-\frac{\pi }{6})$, and the blue graph is the graph of $y=4 \sec (2x-\frac{\pi }{6})$. The period of both functions are the same and equal $\frac{2\pi }{2}=\pi$.