IMO 2009 Shortlist G8
Let ABCD be a circumscribed quadrilateral. Let g be a line through A which meets the segment BC in M and the line CD in ...
Category: Geometry
Problem
Let ABCD be a circumscribed quadrilateral. Let g be a line through A which meets the segment BC in M and the line CD in N. Denote by I1, I2, and I3 the incenters of 4ABM, 4MNC, and 4NDA, respectively. Show that the orthocenter of 4I1I2I3 lies on g.