There are two special kinds of square matrices (n X n matrix) known as the Upper Triangular Matrix & the Lower Triangular Matrix.
Upper Triangular Matrix - Elements below the main diagonal are all zero.
i.e. M[i,j] = 0, for i > j
Lower Triangular Matrix - Elements above the main diagonal are all zero.
i.e. M[i,j] = 0, for i < j
where,
Main diagonal - The diagonal running through M[1,1] to M[n,n] for a nXn square matrix.
Upper Triangular Matrix - Elements below the main diagonal are all zero.
i.e. M[i,j] = 0, for i > j
Lower Triangular Matrix - Elements above the main diagonal are all zero.
i.e. M[i,j] = 0, for i < j
where,
