1、AD=AB=1BE⊥AG,DF⊥AG,即∠AFD=∠BEA=90°∠DAF+∠BAE=90°,∠DAF+∠ADF=90°即∠ADF=∠BAE∴△ABE≌△DAF(AAS)2、∴AF=BE∵DF²+AF²=AD²1/2DF×AF=1/8即2DF×AF=1/2∴DF²+AF²=1DF²+AF²-2DF=1-1/2(DF-AF)²=1/2|DF-AF|=√2/2∵AF=BE∴|DF-BE|=√2/2即|BE-DF|=√2/2