Laplacian in Cartesian CoordinatesLaplacianInCartesianCoordinates2006-10-26 03:22:072009-04-18 14:35:40Definition% this is the default PlanetMath preamble. as your knowledge
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% define commands hereThe Laplacian operator in Cartesian coordinates is
\begin{equation}
\nabla^{2} = \frac{\partial^2}{\partial x^2}+ \frac{\partial^2}{\partial y^2} + \frac{\partial^2}{\partial z^2}
\end{equation}