∵BE平分∠ABC,DF平分∠ADC,
∴∠ABE=∠EBC,∠ADF=∠FDC
又∠ABC+∠ADC=360-90*2=180
∴∠EBC+∠ADF=180/2=90
又∠ABE+∠AEB=90,∠ABE=∠EBC
∴∠EBC+∠AEB=90
则∠AEB=∠ADF
得证BE‖DF