BE⊥CD
∵AB⊥AC,AD⊥AE
∴∠BAC=∠DAE=90°
∴∠BAE=∠DAC
又∵AB=AC,AD=AE
∴△BAE≌△CAD
所以∠D=∠E
根据外角,得∠DAE=∠DFE=90°
∴BE⊥CD