ass="comment">% sym</span>
q       = [ x   y   PSI   ];
dq      = [ dx  dy  dPSI  ];
ddq     = [ ddx ddy ddPSI ];
</pre><h2 id="4">Alternative velocity related variables</h2><p>
<p>However, in many occasions it is more convenient to use the states \(v_{\rm T}\) e \(\alpha_{\rm T}\) instead of \(\dot{x}\) e \(\dot{y}\).</p>
<p>The equations relating this pairs of variables is</p>
<p>
    \begin{eqnarray}
    \nonumber \dot{x} &=& v_{\rm T} \cos \left( \psi + \alpha_{\rm T} \right) \\
    \dot{y} &=& v_{\rm T