(1)如图1,△ABC中,∠BAC=90°,AB=AC,AE是过A点的一条直线,且B、C在AE的异侧,BD⊥AE于D,C
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(1)∵∠BAC=90°,BD⊥AE,CE⊥AE,

∴∠BDA=∠AEC=90°,

∵∠ABD+∠BAE=90°,∠CAE+∠BAE=90°

∴∠ABD=∠CAE,

∵AB=AC,

在△ABD和△CAE中,

∠BDA=∠AEC

∠ABD=∠CAE

AB=AC ,

∴△ABD≌△CAE(AAS),

∴BD=AE,AD=CE,

∵AE=AD+DE,

∴BD=DE+CE;

(2)BD=DE-CE;

∵∠BAC=90°,BD⊥AE,CE⊥AE,

∴∠BDA=∠AEC=90°,

∵AB=AC,

在△ABD和△CAE中,

∠BDA=∠AEC

∠ABD=∠CAE

AB=AC ,

∴△ABD≌△CAE(AAS),

∴BD=AE,AD=CE,

∴AD+AE=BD+CE,

∵DE=BD+CE,

∴BD=DE-CE.

1年前

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