Chapter 7.5, Problem 14P

a) By examining the graphs of $u$ vs. $t$ in Figures $\mathrm{7.5.3}$, $\mathrm{7.5.5}$, and $\mathrm{7.5.7}$, estimate the period $T$ of the van der Pol oscillator in these cases.

b) Calculate and plot the graphs of solutions of the van der Pol equation for other values of the parameter $\mu$. Estimate the period $T$ in these cases also.

c) Plot the estimated values of $T$ versus $\mu$. Describe how $T$ depends on $\mu$.