Hello 1. The problem statement, all variables and given/known data Find the Fourrier coefficients in the annulus problem of the text. uxx+uyy=0 in 0<a²<x²+y²<b² u=g(θ) for x²+y²=a² u=h(θ) for x²+y²=b² 2. Relevant equations The solution is 3. The attempt at a solution I have the solutions but when I solved it for Co and Do I didn't get the same thing, but or all the other coefficients I got the right thing. Here is the problem To get Co and Do I did the integral on both sides from 0 to 2π to get rid of the sum. So I ended up with But the solution give a factor 1/π Before the integral of h and g , why ? Thank you !