Pendulum Phase Plane Applet

An updated version of this demonstration, without Java, is available here.

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).