The Wave Equation

Needs["Calculus`VectorAnalysis`"]

The wave equation without damping in Cartesian coordinates is

(d/dt)^2 u = Div[ c^2 Grad[u]]

waveCartesian := 

	D[u[x,y,t],{t,2}] == Div[c^2 Grad[u[x,y,t]]]

waveCartesian
The superscripts on u represent partial derivatives. For example, u^(2,0,0) is the second derivative with respect to x.

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