Table 1: (a) Harmonic term convergence for various amplitudes (1st resonant frequency). (b) Harmonic term convergence for various amplitudes (2nd resonant frequency).

(a)

Homotopy perturbation No. of harmonic terms = 1 2 3 0.64348 0.64347 0.64347 0.6 0.66140 0.66140 0.66094 0.66091 1 0.67759 0.67759 0.67641 0.67619 1.4 0.68721 0.68721 0.68580 0.68530

(b)

Homotopy perturbation No. of harmonic terms = 1 2 3 1.07786 1.07784 1.07784 0.6 1.19539 1.19539 1.1936 1.19356 1 1.40661 1.40661 1.4005 1.40024 1.4 1.66715 1.66715 1.65219 1.6600