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vuonghongtham07

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C

congchuaanhsang

$\Delta$ DEK ~ $\Delta$ CKM (g.g)

\Rightarrow $\dfrac{CM}{CK}=\dfrac{CM}{DF}=\dfrac{DK}{DE}$

\Leftrightarrow $\dfrac{DF}{DE}=\dfrac{CM}{DK}=\dfrac{CM}{CF}$

\Rightarrow $\Delta$DFE ~ $\Delta$CMF (c.g.c)

\Rightarrow $\hat{DFE}=\hat{CMF}$ \Rightarrow $\hat{EFM}=90^0$

\Leftrightarrow đpcm
 
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