[b]
Def1. Let L be a line in E. We define the "orthogonal projection onto L" to be
Ol = {(P,Q)| P,Q in E and either
1.P lies on L and P=Q or
2.Q is the foot of the perpendicular to L through P.
Problem 1. Let L be a line in E. Show that Ol is not a rigid motion because it fails...