13-2. Class#24 Orthogonal Projections
10-1. Class#18 #3 ~ #8(1st part) Basis and Coordinates
10-2. Class#18 #8~Class#19 #6 isomorphism
11. Class#19 #7~Class#20 Row space of A
9-1. Class#16 #5~Class#17 #3 Subspaces