MathDB

4

Part of 2020 USOJMO

Problems(1)

geo equals ForeBoding For Dennis

Source: USAJMO 2020/4

6/21/2020
Let ABCDABCD be a convex quadrilateral inscribed in a circle and satisfying DA<AB=BC<CDDA < AB = BC < CD. Points EE and FF are chosen on sides CDCD and ABAB such that BE⊥ACBE \perp AC and EF∥BCEF \parallel BC. Prove that FB=FDFB = FD.
Milan Haiman
USAJMOgeometry2020 USAJMOgeometry solvedAngle Chasingeasyusojmo