The diffraction both plane monochromatic wave and ultra short electromagnetic impulse is discussed. At the heart of the solution the method of integral equation in space-frequency and time-space representations is used. Integral equations are solved by the Galerkin’s method with Tchebyshev basis which is everywhere except corner points takes into account the field singularity at the metal edges. Moreover in time-space equations splines are used for approximation of time dependence solution. The methods of effective calculation of matrix elements in the system of linear algebraic equations are discussed. The C# program is worked out. The investigation results are given.