A= [aij] n x n lower triangular matrix
B= [bij] n x n lower triangular matrix
C= [cij] = AB
Proof cij= 0 for i < j or lower diagonal
cij= [ ai1b1j + ai2b2j + ...+ai(j-1)b(j-1)j ] + [ aijbjj +....+ainbnj ]
I am a little confuse of what they are trying to show within the 2 brackets.
nice reply Hacker, thx!
btw, is this thought process correct:
If we multiply a matrix A by a matrix B, assuse dimensions are so that
multiplication is defined, then AB=C, and the columns of C
will be a linear combination of the columns of A, using the the elements in
column j, j=1,....,n as weights ?