完成下列证明过程:已知:如图,AD⊥BC于D,EF⊥BC于F,∠1=∠3,求证:AD平分∠BAC.证明:∵AD⊥BC于DEF⊥BC于F(已知)∴∠ADB=∠EFB=90°( _________ )∴AD∥EF( _________ )∴∠1=∠E( _________ )∠2=∠3( _________ )又∵∠3=∠1(已知)∴∠1=∠2( _________ )∴AD平分∠BAC.