【此题应证明∠BAD=∠CAE】
证明:
∵AB:AD=BC:DE=AC:AE
转化为AB:BC:AC=AD:DE:AE
∴⊿ABC∽⊿ADE
∴∠BAC=∠DAE
∵∠BAD=∠BAC-∠DAC
∠CAE=∠DAE-∠DAC
∴∠BAD=∠EAC