Let α and β be the angles of a non-isosceles triangle ABC at points A and B, respectively. Let the bisectors of these angles intersect opposing sides of the triangle in D and E, respectively. Prove that the acute angle between the lines DE and AB isn't greater than \frac{|\alpha\minus{}\beta|}3. inequalitiestrigonometrycalculusderivativegeometryangle bisectorgeometry unsolved