\frac{\partial {\bf p}_{{\rm R}/{\rm O}}}{\partial q_3}
    \end{eqnarray}
</p>
<p>Thus</p>
<p>
    \begin{eqnarray}
    \nonumber \frac{\partial {\bf p}_{{\rm F}/{\rm O}}}{\partial q_1} &=& \frac{\partial {\bf p}_{{\rm F}/{\rm O}}}{\partial x} = {\bf i} \\
    \nonumber \frac{\partial {\bf p}_{{\rm F}/{\rm O}}}{\partial q_2} &=& \frac{\partial {\bf p}_{{\rm F}/{\rm O}}}{\partial y} = {\bf j} \\
    \nonumber \frac{\partial {\bf p}_{{\rm F}/{\rm O}}}{\partial q_3} &=& \frac{\partial {\bf p}_{{\rm F}/{\rm O}