Italian Mathematical Olympiad 2008
Source: Problem 1
August 23, 2008
geometrycircumcirclegeometry proposed
Problem Statement
Let be a regular dodecagon, let be the intersection point of the diagonals and . Let be the circle which passes through and , and which has the same radius of the circumcircle of the dodecagon, but is different from the circumcircle of the dodecagon. Prove that:
1. lies on
2. the center of lies on the diagonal
3. the length of equals the length of the side of the dodecagon