[Toán 8] chứng minh

N

nhuquynhdat

Ta có: $AH \perp BC; DE \perp BC \Longrightarrow AH//DE \Longrightarrow \dfrac{CE}{HE}=\dfrac{CD}{AD}=\dfrac{CD}{AB}$

CM: $\Delta CDE \sim \Delta ABH (g-g) \Longrightarrow \dfrac{CE}{AH}=\dfrac{CD}{AB}$

$\Longrightarrow \dfrac{CE}{HE}=\dfrac{CE}{AH} \Longrightarrow AH=HE$
 
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