i have a PDE in polar coordinates with 0 < theta < pi/2 and a < r < b

use laplace's equation for the initial conditions u(r,0) = 0, u(r, pi/2) = 0, and u(r,0) = 0 and the boundary condition u(b,theta) = theta

does anyone know how to solve this PDE? i know how to do the fourier series at the end, but how do i get u(r,theta)?