[Toán 7] Chứng minh trong tam giác

T

thewinter

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D

duc_2605

AB > AC \Rightarrow góc B < góc C
DO Ad là phân giác \Rightarrow BAD = DAC
Xét tam giác BAD có: B + BAD + ADB = 180
Xét tam giác DAC có: ADC + C + DAC = ADC + C + BAD = 180
Do B < C \Rightarrow ADB > ADC
 
V

vanmanh2001

Vì : $AB$ > $AC$
\Rightarrow $\widehat{ABC}<\widehat{ACB}\$
Tam giác BAD có $\widehat{ABD}$+$\widehat{BAD}$+$\widehat{BDA}$ = $180^0$
Tam giác DAC có $\widehat{DAC}$+$\widehat{DCA}$+$\widehat{ADC}$
Vì $\widehat{ABC}$<$\widehat{ACB}\$ \Rightarrow $\widehat{BDA}$ > $\widehat{ADC}$
 
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