The geometrical or high‐frequency approximation to solutions of the two‐dimensional wave equation in an inhomogeneous medium is considered. A new ordinary differential equation for a quantity which is inversely proportional to the geometrical high‐frequency field intensity (the square of the field amplitude) is derived. This equation, along with the standard ray and phase equations form a system form which a complete wave solution in the high‐frequency asymptotic limit can be calculated numerically, e.g., through the use of a differential analyzer. The examples of a homogeneous medium and a plane stratified inhomogeneous medium are discussed, and the results of the preceding analysis are verified in these two special cases.