pan></code> which is also our notation
        for the derivative in the source code.
      </p>
<p>
        Ordinary differential equations occur nearly everywhere in natural sciences.
        For example, the whole Newtonian mechanics are described by second order
        differential equations. Be sure, you will find them in every discipline.
        They also occur if partial differential equations (PDEs) are discretized.
        Then, a system of coupled ordinary differential occurs, sometimes also ref