MathDB
IMOC 2018 G4 (parallel wanted, circumcircles, incenter, symmetrics related)

Source: https://artofproblemsolving.com/community/c6h1740825p11314688

March 22, 2020
geometrycircumcircleincenterparallel

Problem Statement

Given an acute ABC\vartriangle ABC with incenter II. Let II' be the symmetric point II with respect to the midpoint of B,CB,C and DD is the foot of AA. If DIDI and the circumcircle of vartriangle BICBI'C intersect at TT and TITI' intersects the circumcircle of ATI\vartriangle ATI at XX. Furthermore, E,FE,F are tangent points of the incircle and AB,AC,PAB,AC, P is the another intersection of the circumcircles of ABC,AEF\vartriangle ABC, \vartriangle AEF. Show that AXPIAX \parallel PI. https://3.bp.blogspot.com/-tj9A8HIR6Vw/XndLEPMRvnI/AAAAAAAALfk/2vw_pZbhpnkTKIc1BcKf4K7SNZ11vu4TACK4BGAYYCw/s1600/2018%2Bimoc%2Bg4.png