证明:连接EF,交AD于O
∵AD平分∠BAC
∴∠BAD=∠CAD
∵DE⊥AB,DF⊥AC,AD=AD
∴△ADE全等于△ADF
∴AE=AF
∵AO=AO,∠BAD=∠CAD
∴△AOE全等于△AOF
∴OE=OF,∠AOE=∠AOF=90
∴AD垂直平分EF
证明:连接EF,交AD于O
∵AD平分∠BAC
∴∠BAD=∠CAD
∵DE⊥AB,DF⊥AC,AD=AD
∴△ADE全等于△ADF
∴AE=AF
∵AO=AO,∠BAD=∠CAD
∴△AOE全等于△AOF
∴OE=OF,∠AOE=∠AOF=90
∴AD垂直平分EF