The triangle ABC has O as its circumcenter, and H as its orthocenter. The line AH and BH intersect the circumcircle of ABC for the second time at points D and E, respectively. Let A′ and B′ be the circumcenters of triangle AHE and BHD respectively. If A′,B′,O,H are not collinear, prove that OH intersects the midpoint of segment A′B′. geometrycircumcircleIndonesiaorthocenterIndonesia MOInamo