Solution
= Solution
Let $a=e^{i\pi/3}$ and $b=e^{-i\pi/3}$. The Möbius map $T(z)=(z-a)/(z-b)$ sends the two circular arcs through $a,b$ to rays bounding a wedge of angle $2\pi/3$. After choosing the branch and a unimodular constant so the interior has positive argument, $f(z)=e^{i\phi}T(z)^{3/2}$ maps that wedge bijectively onto the upper half-plane.