Combined method of calculation of the field of the point source in a wave guide

The two-dimensional problem of propagation of waves, raised by a point source, in an interior wave guide is investigated. The Dirichlet (Neumann) boundary condition is given on the upper (lower) bound of the wave guide. The possibility of representation of the exact solution as a sum of the geometro-optical waves, the normal waves and the residual is shown. The sufficient conditions on the general amount of the detached normal and geometro-optical waves are obtained. The residual is expressed by the simple formula.