David Tran got in touch to say he's also working his way through SOE, and he's posting on http://davidtran.doublegifts.com/blog/, where he's mainly posting solutions, looks good!I discussed some answers on irc with Apocalisp, who has some very subtle versions of regularPolygon and isConvex.  I may, though I still find doing proofs painful-and-not-really-fun try to work [...]