Abstract: Liénard equations of
the form with an even function, are considered in
the weakly nonlinear regime A perturbative algorithm for
obtaining the number, amplitude and shape of the limit cycles of these systems
is given. The validity of this algorithm is shown and several examples
illustrating its application are given. In particular, an approximation for the amplitude of
the van der Pol limit cycle is explicitly obtained.
Keywords and phrases: Liénard equation, limit cycles, weakly nonlinearity.
