paragraph_text: <td><math>\begin{matrix} \boldsymbol{\hat \rho} & = & \sin\vartheta\mathbf{\hat r}+\cos\vartheta\boldsymbol{\hat\vartheta} \\ \boldsymbol{\hat\varphi} & = & \boldsymbol{\hat\varphi} \\ \mathbf{\hat z}      & = & \cos\vartheta\mathbf{\hat r}-\sin\vartheta\boldsymbol{\hat\vartheta} \\ \end{matrix}</math>