证明：∵等边△ABC∴∠A＝∠B＝∠ACB＝60∵DE//AB∴∠EDC＝∠A＝60，∠DEC＝∠B＝60∵DF⊥DE∴∠EDF＝90∴∠F＝90-∠DEC＝30, ∠CDF＝∠EDF-∠EDC＝30∴∠CDF=∠F
