If we are given a square matrix (i.e., a matrix with equal number of rows and columns), we can classify it as the diagonal matrix if only its diagonal elements are nonzero; as an upper triangular...

If we are given a square matrix (i.e., a matrix with equal number of rows and columns),

we can classify it as the diagonal matrix if only its diagonal elements are nonzero; as

an upper triangular matrix if all the elements below the diagonal are 0; and as a lower

triangular matrix if all elements above the diagonal are 0. Some examples are:

Diagonal matrix: