09. Dot products, accessible version 9.47
10. Dot product 2: transposition, accessible version 9.09
11. Dot product 3: orthogonal matrices, accessible version 15.14
12. Rotations, accessible version 17.41
13. Simultaneous equations and row operations, accessible version 18.53
14. Echelon form, accessible version 10.31
15. Reduced echelon form, accessible version 14.16
16. Echelon examples, accessible version 14.17