Let w be the circumcircle of non-isosceles acute triangle ABC. Tangent lines to w in A and B intersect at point S. Let M be the midpoint of AB, and H be the orthocenter of triangle ABC. The line HA intersects lines CM and CS at points Ma and Sa, respectively. The points Mb and Sb are defined analogously. Prove that MaSb and MbSa are the altitudes of triangle MaMbH. geometrycircumcirclegeometry unsolved