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Starting with an old socks-in-the-drawer riddle, we will work our way up to the Happy Ending Theorems of Esther Klein, Paul Erdos, and George Szekeres: given any integer p that is greater than or equal to 4, any sufficiently large set of points in the plane such that no three points are on the same line must contain a subset of p points which are the vertices of a convex p-sided polygon.
The main tools which will be developed along the way are the pigeonhole principle and its muscular consequence, Ramsey theory. |
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