BE⊥EF.理由如下：(更正：DF=（1/4）DC.）设正方形边长AB=4,△ABE中：AB=4,AE=2,BE=2√5.△DEF中：DE=2,DF=1,EF=√5,∴△ABE∽△DEF.∴∠ABE=∠DEF.∵∠ABE+∠AEB=90°,∴∠DEF+∠AEB=90°,∴∠BEF=90°,∴BE⊥EF.且...