Is that Prove A times the identity is the identity times A?
How do you prove this:
The matrix multipication definition I have is:
Given A = (aij) : m x n matrix
B = (bij) : n x p matrix
We define the product C = AB where C has general element cij = n sigma k=1 aikbkj
=ai1bij + ai2b2j + ai3b3 + .. + ainbnj
I don't quite understand the final line though. I understand everything up to that, but not quite how you get to the final part of the proof ..