I need a function describing another curve.

Question

I already asked for a function here and the answers where very helpful. But know I need a function for this curve:

the curve

It like my first curve but rotated by 90 and inverted horizontally.

Tank you :)

Update The answer tan(πx/2) is good. But I need to modify this curve to be sharper (closer to the x axis for low values) and I currently do not get to modify it like this.

Answer 1

Since tan(x) goes through (0, 0), goes to infinity as x goes to $\frac{\pi}{2}$, and goes to negative infinity as x goes to $-\frac{\pi}{2}$, $y= tan(\frac{\pi}{2}x)$ should do nicely.

Answer 2

Another obvious option would be $\text{arctanh }x$.