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%\section{A generic matrix}
Notice the use of vertical and diagonal dots in the generic matrix
shown below.
$$A=\pmatrix{a_{1 1}&a_{1 2}&\ldots&a_{1 n}\cr
             a_{2 1}&a_{2 2}&\ldots&a_{2 n}\cr
             \vdots&\vdots&\ddots&\vdots\cr
             a_{m 1}&a_{m 2}&\ldots&a_{m n}\cr}$$

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