Let triangle ABC square at A(AB < AC) . Let D and E be the midpoints of the lines BC and AC respectively. Draw DF perp AB at F. Let O be the intersection of AD and FE. a. What is the quadrilateral AFDE? Prove. b. Let I be the point symmetrical to D about AC. Prove that DI is the bisector of angle ADC. C. Draw AH as altitude of triangle ABC Prove angle FHE is right angle