Angle bisectors of angles by vertices A, B and C in triangle ABC intersect opposing sides in points A1, B1 and C1, respectively. Let M be an arbitrary point on one of the lines A1B1, B1C1 and C1A1. Let M1, M2 and M3 be orthogonal projections of point M on lines BC, CA and AB, respectively. Prove that one of the lines MM1, MM2 and MM3 is equal to sum of other two geometryangle bisectororthogonal projection