ABC is a triangle and AA′ , BB′ and CC′ are three altitudes of this triangle . Let P be the feet of perpendicular from C′ to A′B′ , and Q is a point on A′B′ such that QA \equal{} QB . Prove that :
\angle PBQ \equal{} \angle PAQ \equal{} \angle PC'C geometryangle bisectorgeometry proposed