الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 73 |  |  |
| | | from | 73 | | |
Abstract
In the work presented in this thesis, we give expressions for the periodic solution of (0.1) and its frequency up to the fourth term using the perturbation method, also we consider the perturbed Van der pol’s equation (1.1). A detailed study for a D - periodic solution of (1.1) is considered.