[math-fun] Tetrahedral Centers

Since this has come up, here's a long time question I've had.... Take a random tetrahedron. For a given triangle center, connect it to the opposing corner of the tetrahedron. Repeat for each face of the tetrahedron. For which triangle centers are the 4 lines concurrent? If X333 had that property, I suppose Y333 would be a fine name for that Tetrahedral center. Links: http://faculty.evansville.edu/ck6/encyclopedia/ETC.htmlhttp://bernard.gibert... Ed Pegg Jr