Given a set of 9 points, no 3 collinear, prove there must be a subset of 5 that forms a convex pentagon.

This problem, along with 8 points no convex pentagon and 5 points to convex quad are parts of the Happy Ending problem and its generalization, see http://en.wikipedia.org/wiki/Happy_Ending_problem

(I think this particular problem is a little too ambitious for Perplexus members)

Posted by Brian Smith on 2009-10-18 00:54:51