BD = (1/2)AB ；已知,2CD = 3AB ,可得：CD = (3/2)AB ；已知,E,F为CD的三等分点,可得：DF = (1/3)CD = (1/2)AB = AD = BD ；则有：△ADF和△BDF都是等腰直角三角形,可得：∠AFD = ∠BFD = 45° ；所以,∠AFB = ∠AFD...