We study the mixed Dirichlet–Neumann problem for Laplace equation in complement of a bounded convex polygonal quadrilateral extended complex plane. The Dirichlet / Neumann conditions at opposite pairs sides are $$\{0,1\}$$ and $$\{0,0\},$$ resp. solution to this is harmonic function unbounded polygon known as potential quadrilateral. compute values u including its value infinity. main result pa...