10-327/Classnotes for Thursday October 21

See some blackboard shots at BBS/10_327-101021-143325.jpg.

 Dror's notes above / Student's notes below

Here are some lecture notes..

Riddle Along

Can you color $\mathbb{R}^2$ with 4 colors such that no points with distance one are the same color? Sorry, I meant 3, not 4!