11.4 Let AA1 and BB1 are altitudes of an acute non-isosceles triangle ABC, A′ is a midpoint of BC and B′ is a midpoint of AC. A segement A1B1 intersects A′B′ at point C′. Prove that CC′⊥HO, where H is a orthocenter and O is a circumcenter of ABC.
(L. Emel'yanov) geometrycircumcirclepower of a pointradical axisgeometry proposed