Solve Laplace's equation σ^2u/σr^2 + 1/r σu/σr + 1/r^2 σ^2u/σθ^2 = 0
inside the quarter - circle of radius 1 ( 0 ≤ θ ≤ π/2, 0 ≤ r ≤ 1) subject to the boundary conditions: a. u(r,0) = 0, u(r,π/2)=0, σu/σr (1,θ)=f(θ)
b. σu/σθ = 0, u(r,π/2)=0, u (1,θ)=f(θ)