MathDB

G4

Part of 2016 IMO Shortlist

Problems(1)

Reflect incenter through side of isosceles triangle

Source: 2016 IMO Shortlist G4

7/19/2017
Let ABCABC be a triangle with AB=AC≠BCAB = AC \neq BC and let II be its incentre. The line BIBI meets ACAC at DD, and the line through DD perpendicular to ACAC meets AIAI at EE. Prove that the reflection of II in ACAC lies on the circumcircle of triangle BDEBDE.
geometryincenterreflectioncircumcirclegeometry solvedIMO ShortlistInversion