AD=2AE,证明如下
延长AE至F,使EF=AE
AB=BC
∠BAC=∠BCA,∠BAE=∠ADC
∠BAC-∠BAE=∠BCA-∠ADC
∠EAC=∠CAD
易证⊿BFE≌⊿CAE
∠BFE=∠EAC=∠CAD
AC=BF
易证⊿ABF≌⊿ACD
AE=1/2AF=1/2AD
AD=2AE,证明如下
延长AE至F,使EF=AE
AB=BC
∠BAC=∠BCA,∠BAE=∠ADC
∠BAC-∠BAE=∠BCA-∠ADC
∠EAC=∠CAD
易证⊿BFE≌⊿CAE
∠BFE=∠EAC=∠CAD
AC=BF
易证⊿ABF≌⊿ACD
AE=1/2AF=1/2AD