Phase portrait of the driven, damped nonlinear pendulum θ̈ + γθ̇ + sin(θ) = F·cos(ωt). The separatrix (energy E=2) divides libration from rotation. With driving, trajectories can become chaotic. Click canvas to add initial conditions. Poincaré section reveals the strange attractor.
Phase portrait (θ vs θ̇) — click to add trajectory