Hi everyone, I would need to get some help on the following question Let A (m*n) Let B (m*p) Let L(A) be the span of the columns of A. L(A) is orthogonal to L(B) <=> A'B=0 I suppose that the => direction is pretty obvious, since A is in L(A) and B in is L(B). Now I am not sure how to attack the <= statement. I guess that every vector in L(A) is generated by the rows of A, and every vector in L(B) is generated by the columns of B. Therefore A'B=0, means Sum(i, j, constant_i*row_i of A*constant_j*row_j of B). How can I improve my argument?