∵∠BFE=90°
∴∠AFB+∠DFE=90°
∵∠AFB+∠ABF=90°
∴∠ABF=∠DFE
∵∠A=∠D
∴∠AFB=∠FED
∴△ABF∽△DFE
∴BF/EF=AF/DE
即
(√6^2+2^2)/EF=2/3
得：EF=3√10