[Toán 8]Chứng minh bdt tam giác

M

minhhieu0702

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B

babu_m.a

Ta có: AB = BD =>
[TEX]\Delta ABD[/TEX] cân tại B
[TEX]\Rightarrow[/TEX] ^ DAB = ^ ADB
[TEX]\Rightarrow[/TEX] ^ ADB+ ^ BDC > ^ DAB - ^ BAC
hay ^ADC > ^ DAC
[TEX]\Delta ADC[/TEX] có:^ ADC > ^ DAC
[TEX]\Rightarrow AC > DC ( qh..)[/TEX]
 
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