t
    torque</h1>

    <p> Let us first consider the dynamics of the pendulum if it is driven in a
    particular simple way: a torque which does not vary with time:
    \begin{equation} ml^2 \ddot\theta + b\dot\theta + mgl \sin\theta = u_0.
      \end{equation} </p>.


    <example><h1>Simple Pendulum in Python</h1>

      <p>You can experiment with this system in <drake></drake> using</p>

      <script>document.write(notebook_link('pend'))</script>

    </example>

    <p> These are relatively simple dif