The van der Pol's equation is a second-order nonlinear differential equation which has been used to describe (among other systems) action potentials in neurons, beating of the heart and circadian rhythm. The equation may be expressed as two first-order ODEs as follows: dx_1/dt = x_2 dx_2/dt = epsilon (1 - x_1^2) x_2 - b^2 x_1 Solve the ODEs in MATLAB and make a phase plane plot (i.e. x1 vs. x2) for x_1 (0) = 0, x_2 (0) = 1 with b = 1 and epsilon = 0.5