MathDB
Constant point

Source: Iran PPCE 2007

March 23, 2007
geometry proposedgeometry

Problem Statement

Let (C)(C) and (L)(L) be a circle and a line. P1,,P2n+1P_{1},\dots,P_{2n+1} are odd number of points on (L)(L). A1A_{1} is an arbitrary point on (C)(C). Ak+1A_{k+1} is the intersection point of AkPkA_{k}P_{k} and (C)(C) (1k2n+11\leq k\leq 2n+1). Prove that A1A2n+2A_{1}A_{2n+2} passes through a constant point while A1A_{1} varies on (C)(C).