是。∎AEDF→AF//DE；DF//AE→∠ADE=∠DAF；∠ADF=∠DAE 而∠DAF=∠DAE 所以∠ADE=∠ADF
是DE//AB，∴ ∠EDA=∠DABDF//AC，∴ ∠FDA=∠CAD又AD平分∠CAB，∴ ∠CAD=∠DAB∴ ∠EDA=∠FDA∴DO是△DEF的角平分线
