1. The Dirichlet problem for the exterior of a circle is =0 on {(x,y) E R? : x + y > a} u =h on {(x, y) E R : x + y = a} Uz1 + Uy,y lim sup |u(x, y) CC < Derive the Poisson formula in polar coordinates for this problem: p2 a? 27 (r, 0) a? 2ar cos(0 4) + r2 d - where h(0) = h(a cos 0, a sin 0). Hint: Follow the derivation of the Poisson formula on the disk Ba(0).