Fig. 1

a Comparison of approximate periodic solution of Eq. (7) obtained by present method (denoting by circles) with numerical solution obtained by fourth order Runge–Kutta method (denoted by solid line) for A = 1. b Comparison of approximate periodic solution of Eq. (7) obtained by present method (denoting by circles) with numerical solution obtained by fourth order Runge–Kutta method (denoted by solid line) for A = 10