Problem

Source: CRMO 2015 region 4 (Karnataka) p1

Tags: geometry, Circumcenter, incenter, reflection



Let \(ABC\) be a triangle. Let \(B'\) denote the reflection of \(b\) in the internal angle bisector \(l\) of \(\angle A\).Show that the circumcentre of the triangle \(CB'I\) lies on the line \(l\) where \(I\) is the incentre of \(ABC\).