如图①,在△ABC中,AB=AC,∠BAC=90°,AN是过A点的任意一条直线,BD⊥AN...答:1 ∵∠C=90°,BD⊥AE,CE⊥AE ∴∠BAD+∠EAC=∠CAE+∠ACE=90° ∴∠BAD=∠ACE,∠BDA=∠AEC ∵AB=AC ∴△ABD≌△CAE ∴AE=BD,AD=EC ∴DE=AE-AD=BD-EC 2 存在 ∵∠C=90°,BD⊥AE,CE⊥AE ∴∠BAD+∠EAC=∠CAE+∠ACE=90° ∴∠BAD=∠ACE,∠BDA=∠AEC ∵AB=AC ∴△ABD≌...