Diagonal Matrices

Diagonal matrices are matrices that have non-zero numbers in the diagonal only. The diagonal of a matrix contains all numbers in the straight line from the top left to the bottom right numbers.

Example

$$ \begin{bmatrix} 3 & 0 & 0 \\ 0 & 7 & 0 \\ 0 & 0 & 5 \end{bmatrix} $$