here.  do a
      python demo in class -->

    </section> <!-- undamped constant torque -->

    <p>Before we continue, let me now give you the promised example of a system
    that is not stable i.s.L., but which attracts all trajectories as time
    goes to infinity. We can accomplish this with a very pendulum-like example
    (written here in polar coordinates):</p>

    <example><h1>Unstable equilibrium point that attracts all trajectories</h1>

      <p>Consider the system \begin{align*} \dot{r} &= r(