IMO 2017 Shortlist G5
Let ABCC1B1A1 be a onvex hexagon su h that AB “ BC, and suppose that the line segments AA1, BB1, and CC1 have the same p...
Category: Geometry
Problem
Let ABCC1B1A1 be a onvex hexagon su h that AB “ BC, and suppose that the line segments AA1, BB1, and CC1 have the same perpendi ular bise tor. Let the diagonals AC1 and A1C meet at D, and denote by ω the ir le ABC. Let ω interse t the ir le A1BC1 again at E ‰ B. Prove that the lines BB1 and DE interse t on ω. (Ukraine)