∠BAD = 180°-∠BAC-∠CAE = 180°-90°-∠CAE = 90°-∠CAE = ∠ACE ；因为,在△ABD和△CAE中,∠ADB = 90° = ∠CEA ,∠BAD = ∠ACE ,AB = CA ,所以,△ABD ≌ △CAE ,可得：AD = CE ,BD = AE ,所以,DE = AE+AD = B...