S.B. Waluy a, W.T. Van Horssen
In this paper a nonlinear oscillator problem will be studied. It will be shown that the recently developed perturbation method based on integrating vectors can be used to approximate first in integrals and periodic solutions. The existence, uniqueness, and stability of time-periodic solutions are obtained by using the approximations for the first integrals.
Dept. of Applied Math. Analysis, Faculty of Info. Technol. and System, Delft Univ. of Technology, 2628 CD Delft, Mekelweg 4, Netherlands; Mathematics Department, Semarang State University, Semarang, India