∵△AGF≌△EBD
{等量减等量差相等AG=EB;同位角∠A=∠BED,∠AGF=∠B;两角夹一边},
故GF=BD{对应边相等};
∴DF∥AB{一组对边平行且相等GF=∥BD,GFDB为平行四边形}.