Existence And Multiplicity Of Periodic Solutions For Non-autonomous Second Order System

In this paper, we discuss the existence and multiplicity of periodic solutions for the non-autonomous second order systemIn Setion One,we give the remarks on the cited reference and relate the developments of the existence of periodic solutions for the non-autonomous second order system.The next section ,the fundamental knowledge is given. We contrast the new results of this pape with the former results.In the third section ,the existence of periodic solution is obtain by using the reduction methods and minmax theory.In Section Four ,we obtain the new results about the multiplicity of periodic solution for the non-autonomous second order system by using the reduction methods and the critical point theory.