Higher triangular needs to be interpreted as obtaining only zero entries underneath the primary diagonal, which starts in the higher still left corner. Example[edit] If a square, invertible matrix has an LDU (factorization with all diagonal entries of L and U equivalent to 1), then the factorization is exclusive.[5] http://french-maids74.alltdesign.com/5-simple-statements-about-how-t-u-an-l-b-d-explained-16126363