延长DF,作AM//BD交DF延长线于M,《AFM=〈BFD（对顶角）,〈AMF=〈FDB（内错角相等）,△AMF∽ △BDF,AF/BF=AM/BD,AM=2*5/4=5/2,〈AEM=〈CED（对顶角相等）,AE=CE,〈MAE=〈ECD（内错角相等）,△AME≌△CED,（ASA）∴CD=A...