摘要
By the averaging method of frst order, we study in this work the limit cycles for a class of second order diferential equations and Dufng diferential equations which can be seen as a particular perturbation of the harmonic oscillator.
By the averaging method of frst order, we study in this work the limit cycles for a class of second order diferential equations and Dufng diferential equations which can be seen as a particular perturbation of the harmonic oscillator.