Answer
The period is $4\pi$
Work Step by Step
To find the period, one must first find $b$ in the base equation of secant functions $f(x)=a\cdot $sec$(b(x-c))+d$, then use $\frac{2\pi}{b}$. In this case, $b$ is $1/2$, so the period is $\frac{2\pi}{1/2}=4\pi$
