Let $D$ be the quarter plane where $-\frac\pi4 < \arg(z) < \frac\pi4$. By Riemann mapping theorem, there exists a holomorphic bijection from the open unit disk to $ D$ where $f(0)=1$ and $f'(0)>0$. Calculate explicitly the inverse of this function.
I am thinking maybe I can use the Cayley transform, but this is half the plane not a quarter.