[Toán 9]Tam giác đồng dạng

B

beconvaolop

S

soicon_boy_9x

$\Delta OAB \sim \Delta OEF (g.g)$

$\rightarrow \dfrac{S_{\Delta OAB}}{S_{\Delta OEF}}=\dfrac{b^2}
{EF^2}$

Tương tự $\dfrac{S_{\Delta OBC}}{S_{\Delta OEF}}=\dfrac{a^2}
{EF^2}$

$\rightarrow \dfrac{\Delta OAB}+\Delta OBC}}{S_{\Delta
OEF}}=\dfrac{a^2+b^2}{EF^2}$

$\leftrightarrow \dfrac{a^2+b^2}{EF^2}=2$

$\rightarrow dpcm$

 
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