RESUMEN

A wide class of nonlinear equations is studied in the geometrical optics approximation. It is shown that a nonlinear equation with coefficients dependent on the amplitude of the function sought can be reduced to a system of quasi-linear equations of the gas-dynamics type. As an illustration, the Hamilton--Jacobi equation with a specific form of the nonlinear operator has been solved, and the propagation of monochromatic waves and of point source radiation in nonlinear media has been studied.