MathDB
12nd ibmo - mexico 1997/q2.

Source: Spanish Communities

April 22, 2006
geometryincentercircumcircleinradiustrapezoidgeometric transformationrotation

Problem Statement

In a triangle ABCABC, it is drawn a circumference with center in the incenter II and that meet twice each of the sides of the triangle: the segment BCBC on DD and PP (where DD is nearer two BB); the segment CACA on EE and QQ (where EE is nearer to CC); and the segment ABAB on FF and RR ( where FF is nearer to AA).
Let SS be the point of intersection of the diagonals of the quadrilateral EQFREQFR. Let TT be the point of intersection of the diagonals of the quadrilateral FRDPFRDP. Let UU be the point of intersection of the diagonals of the quadrilateral DPEQDPEQ.
Show that the circumcircle to the triangle FRT\triangle{FRT}, DPU\triangle{DPU} and EQS\triangle{EQS} have a unique point in common.