证明：延长AE至F,使EF=AE,连结BF,DF因AE=EF,BE=ED得ABFD为平行四边形DF=AB,又AB=BD=DC得DF=DC同时也得∠BDF=∠ABD则∠ADC=∠BAD+∠BDF而∠ADF=∠ADB+∠BDF∠BAD=∠BDA得∠ADF=∠BAD+∠BDF所以∠ADC=∠ADF又AD=AD所以...