what is a lower triangular matrix
Unit triangular matrix where all the diagonal are one. A lower triangular matrix is unit lower triangular if it has ones on the diagonal and each and every element above the diagonal element is zero. Unit lower triangular matrix is of the form: A = $\begin{bmatrix}1 & 0 &0 & . & . & 0\\a_{21}& 1 & 0 & .