Let $F$ be a field. A diagonal matrix is a square matrix of the form
\[ \pmatrix{ \alpha_{11} & 0 & \ldots & 0 \cr 0 & \alpha_{22} & \ldots & 0 \cr \vdots & \vdots & \ddots & \vdots \cr 0 & 0 & \ldots & \alpha_{nn} \cr } \]
i.e. in which all but the diagonal elements \(\alpha_{ii}\in F\) for $i=1,\ldots,n$ equal zero.
Examples: 1
