   <span class="emphasis"><em>x'(t) = f(x,t)</em></span>, <span class="emphasis"><em>x(0) = x0</em></span>.
      </p>
<p>
        <span class="emphasis"><em>x</em></span> and <span class="emphasis"><em>f</em></span> can be vectors and the
        solution is some function <span class="emphasis"><em>x(t)</em></span> fulfilling both equations
        above. In the following we will refer to <span class="emphasis"><em>x'(t)</em></span> also
        <code class="computeroutput"><span class="identifier">dxdt</s