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春芽
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仅提供思路:
由角平分线性质:
知
DAI=EAI
又
AI=AI,AID=AIE=90
=>
三角形DAI全等于EAI
所以:DI=EI,ADI=AEI
=>
BDI=CEI
连BI,CI,
BID = ADI-ABI = 90-DAI-ABI = 90 -1/2(BAC+ABC)
=90-1/2(180-ACB)
=1/2ACB
=ACI
=>
BDI相似于IEC
=>
DI/CE = BD/IE
=>
DI^2 = DI*IE = BD*CE
1年前
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