证明：如图，延长BD交CA的延长线于F，∵∠BAC=90°∴∠BAF=∠BAC=90°，∠ACE+∠AEC=90°，∵∠BDC=90°∴∠BDC=∠FDC=90°∴∠ABF+∠BED=90°∵∠AEC=∠BED∴∠ACE=∠ABF∵AB=AC∴△ACE≌△ABF（ASA）∴CE=BF∵CD平...