awesome how prof. Strang uses an error in lecture 9 to draw attention to the fact that the R(C(A)) = R(C(A')) ... a lot of ego driven profs. would have simply shrugged it off.####[['prof. Strang', 'Instructor', 'POS'], ["the R(C(A)) = R(C(A'))", 'Mathematical_Related_Concept', 'POS']]