Answer
$f(x) = sec~4x$
Work Step by Step
The graph has the general shape of a secant graph.
However, compared with the standard secant graph, the first positive asymptote occurs at $x = \frac{\pi}{8}$ instead of $x = \frac{\pi}{2}$. Therefore, we need to include an angle of $4x$ in the function.
The equation is: $f(x) = sec~4x$
