This example demonstrates the behaviour of a non-autonomous system of ODEs \[\begin{align*} f_1(t,x,y)=&\dot x(t) = y\\ f_2(t,x,y) = & \dot y(t) = x-x^3-\frac14 y-A\sin(t)\end{align*}\] with \(A\in\mathbb{R}\).