It is known that triangle ABC is not isosceles with altitudes of AA1,BB1, and CC1. Suppose BA and CA respectively points on BB1 and CC1 so that A1BA is perpendicular on BB1 and A1CA is perpendicular on CC1. Lines BACA and BC intersect at the point TA . Define in the same way the points TB and TC . Prove that points TA,TB, and TC are collinear. geometrycollinearaltitudes