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Wave Equation in two Dimensions

We have now the following discretized partial derivatives \begin{equation*} u_{xx}\approx \frac{u_{i+1,j}^l-2u_{i,j}^l+u_{i-1,j}^l}{h^2}, \end{equation*} and \begin{equation*} u_{yy}\approx \frac{u_{i,j+1}^l-2u_{i,j}^l+u_{i,j-1}^l}{h^2}, \end{equation*} and \begin{equation*} u_{tt}\approx \frac{u_{i,j}^{l+1}-2u_{i,j}^{l}+u_{i,j}^{l-1}}{\Delta t^2}, \end{equation*} which we merge into the discretized 2+1 -dimensional wave equation as \begin{equation} \tag{25} u_{i,j}^{l+1} =2u_{i,j}^{l}-u_{i,j}^{l-1}+\frac{\Delta t^2}{h^2}\left(u_{i+1,j}^l-4u_{i,j}^l+u_{i-1,j}^l+u_{i,j+1}^l+u_{i,j-1}^l\right), \end{equation} where again we have an explicit scheme with u_{i,j}^{l+1} as the only unknown quantity.