∵∠BAC=∠DAE=90°
∴∠BAD-∠DAC=∠DAE-∠DAC,即∠BAD=∠CAE
在△ABD与△ACE中,
∵AB=AC
∠BAD=∠CAE
AD=AE
∴△ABD≌△ACE
∴BD=CE
如不懂,