[ª] , [©] , [^] , [¨]Tracks of incenterEexcenter / Track of excenter(GC World : Various Problems ,Something strange?)
There is a circle O and the corners of ĢABC are on the circle.
An excenter opposite to point C is named I1.
Please find the track of I1 when point A moves on the circle.

GC/Win


Forum of Geometric Constructor by Y.Iijima