
 Pappus's hexagon theorem  Wikipedia, the free encyclopedia 
  Pappus's hexagon theorem (attributed to Pappus of Alexandria) states that given one set of collinear points A, B, C, and another set of collinear points a, b, c, then the intersection points x, y, z of line pairs Ab and aB, Ac and aC, Bc and bC are collinear. 
  The dual of this theorem states that given one set of concurrent lines A, B, C, and another set of concurrent lines a, b, c, then the lines x, y, z defined by pairs of points resulting from pairs of intersections A∩b and a∩B, A∩c and a∩C, B∩c and b∩C are concurrent. 
  A generalization of this theorem is Pascal's theorem, which was discovered by Blaise Pascal at the age of 16. 
 en.wikipedia.org /wiki/Pappus's_hexagon_theorem (379 words) 
