补充:在△ABC中,角BAC=90°.
证明:∵∠ABD+∠BAD=90°;∠CAE+∠BAD=90°.
∴∠ABD=∠CAE.
又∠BDA=∠AEC=90°;AB=AC,则:⊿BDA≌ΔAEC(AAS).
故:BD=AE;AD=CE.
所以,BD=AE=AD+DE=AD+CE.
补充:在△ABC中,角BAC=90°.
证明:∵∠ABD+∠BAD=90°;∠CAE+∠BAD=90°.
∴∠ABD=∠CAE.
又∠BDA=∠AEC=90°;AB=AC,则:⊿BDA≌ΔAEC(AAS).
故:BD=AE;AD=CE.
所以,BD=AE=AD+DE=AD+CE.