Pendulum Phase Plane Applet

This applet draws numerical aproximations to the phase curves for the system of differential equations

This system is equivalent to the second-order equation
the equation of a pendulum. Clicking on a any point in the applet begins a phase curve at that point. The Continue button will continue a curve from its final point. You may choose to use either Euler's method (drawn in red), a Runge-Kutta method of order 2 (drawn in green), or a Runge-Kutta method of order 4 (drawn in blue).