4.7.10 Upper Triangular Matrices
Definition 4.7.16 A matrix M, is upper triangular if Mij = 0 whenever i > j. Thus
such a matrix equals zero below the main diagonal, the entries of the form Mii as shown.
A lower triangular matrix is defined similarly as a matrix for which all entries above the
main diagonal are equal to zero.
With this definition, here is a simple corollary of Theorem 4.7.13.
Corollary 4.7.17 Let M be an upper (lower) triangular matrix. Then det
is obtained by taking the product of the entries on the main diagonal.