\documentclass[preview]{standalone}
\usepackage{tabu}
\begin{document}
{\tabulinesep=1.2mm
\begin{tabu} {|c|c|}
\hline
Cylindrical & $\displaystyle{{1 \over \rho}{\partial \over \partial\rho}\left(\rho {\partial f \over \partial \rho}\right)
+ {1 \over \rho^2}{\partial^2 f \over \partial \phi^2} + {\partial^2 f \over \partial z^2}}$\\\hline
Spherical & $\displaystyle{{1 \over r^2}{\partial \over \partial r}\!\left(r^2 {\partial f \over \partial r}\right)
\!+\!{1 \over r^2\!\sin\theta}{\partial \over \partial \theta}\!\left(\sin\theta {\partial f \over \partial \theta}\right)
\!+\!{1 \over r^2\!\sin^2\theta}{\partial^2 f \over \partial \phi^2}}$\\\hline
\end{tabu}}
\end{document}