Answer
$y = 1-2~cot~[~2~(x+\frac{\pi}{2})~]$
We can see the graph below.
Work Step by Step
$y = 1-2~cot~[~2~(x+\frac{\pi}{2})~]$
When $x = 0$, then $y = 1-2~cot~\pi~~$ (which is undefined)
When $x = \frac{\pi}{8}$, then $y = 1-2~cot~\frac{5\pi}{4} = -1$
When $x = \frac{\pi}{4}$, then $y = 1-2~cot~\frac{3\pi}{2} = 1$
When $x = \frac{3\pi}{8}$, then $y = 1-2~cot~\frac{3\pi}{4} = 3$
When $x = \frac{\pi}{2}$, then $y = 1-2~cot~2\pi$ (which is undefined)
We can see the graph below.