Is there a trick to make Mathematica solve $ $ {\frac {\partial^{2} u}{\partial {x}^{2}}} +{\frac {\partial ^{2} u}{\partial {y}^{2}}} =0$ $ with one boundary condition at $ \infty$ ? Boundary conditions are $ $ \begin{align*} u \left( 0,y \right) &=\cos \left( y \right) \ u \left( x,0 \right) &=0 \ u \left( x,a \right) &=0\Read more