paragraph_text: <td><math>\begin{matrix} \displaystyle{1 \over r\sin\vartheta}\left({\partial \over \partial \vartheta} \left( A_\varphi\sin\vartheta \right)   - {\partial A_\vartheta \over \partial \varphi}\right) \boldsymbol{\hat r} & + \\ \displaystyle{1 \over r}\left({1 \over \sin\vartheta}{\partial A_r \over \partial \varphi}   - {\partial \over \partial r} \left( r A_\varphi \right) \right) \boldsymbol{\hat \vartheta} & + \\ \displaystyle{1 \over r}\left({\partial \over \partial r} \left( r A_\vartheta \right)   - {\partial A_r \over \partial \vartheta}\right) \boldsymbol{\hat \varphi} & \ \end{matrix}</math>