如图,已知:BD⊥AC,EF⊥AC,D、F为垂足,G是AB上一点,且∠l=∠2.
求证:∠AGD=∠ABC.

证明:∵BD⊥AC,EF⊥AC(已知)∴∠BDC=∠EFC=90°(垂直的性质)∴BD//EF(              )∴∠2=∠3(                 )又∵∠l=∠2(已知)∴∠1=∠3(                     )∴GD//BC(                   )∴∠AGD=∠ABC(                   )①同位角相等,两直线平行;②等量代换;③内错角相等,两直线平行;④两直线平行,同位角相等;⑤两直线平行,内错角相等;⑥同旁内角互补,两直线平行;⑦两直线平行,同旁内角互补以上空缺处依次填写正确的顺序为()