This week I gave a talk at UCLA on some aspects of polymath1 project, and specifically on the three new combinatorial proofs of the density Hales-Jewett theorem that have been obtained as a consequence of that project. (There have b...
Todd at Topological Musings has posted an elementary proof of the Hairy Ball Theorem: the theorem that all vector fields on a even-dimensional sphere must vanish somewhere. The elementary proof is by Milnor.
1. Do you guys know of any proofs for the Rotation of Axes to Eliminate an x-y Term theorem? My book doesn't give any proofs for this, but just gives me the equation. It says:(Let's pretend @ is theta.)"The general second-degree ...
