Periodic Solutions of van der Pol\´s Equations with Large Damping Coefficient

A method of computing a periodic solution of van der Pol\´s equation is devised reducing the problem to the solution of a certain equation by means of Newton\´s method. For computing the value of the derivative necessary to apply Newton\´s method, the properties of variation of the orbit in the phase plane are used and, for step-by-step numerical integration of differential equations, a somewhat new method based on Stirling\´s interpolation formula combined with an ordinary Adams\´ extrapolating integration formula is used. The periodic solutions are actually computed for and the minute but important change of the amplitude described by van der Pol\´s equation is found.