I'm supposed to be working with block matrices to solve a problem but I can't visualize what I'm supposed to be looking for. The problem is B=ATA, show that bsubij=avectorsubiT times avectorsubj (sorry I don't know how to use latex). I understand matrix multiplication and what a transpose is but 1) i dont know what bsubij means (does it mean any general element in B? If so, what am I supposed to do with it?) 2) is avectorsubiT the transpose of any given row from A? If so, how is this relevant? 3) is avectorsubj any given column of a? If so, how is this relevant?
I feel that some graphical view of where such i,j elements lie would help me understand this problem a lot more. I would appreciate any help.