(本题6分)如图,点E在直线DF上,点B在直线AC上,若∠AGB=∠EHF,∠C=∠D,则∠A=∠F,请说明理由.
解:∵∠AGB=∠EHF______________
∠AGB=_____________(对顶角相等)
∴∠EHF=∠DGF
∴DB//EC___________________________
∴___________=∠DBA(两直线平行,同位角相等)
又∵∠C=∠D
∴∠DBA=∠D
∴DF//__________________(内错角相等,两直线平行)
∴_______________