toán hình 9

H

hien_vuthithanh

tính được BC=20cm(pitago)
$AB^2$=BH.BC\Rightarrow BH=$\dfrac{AB^2}{BC}=\dfrac{12^2}{20}$=7.2
HC=BC-BH=20-7.2=12.8
$\dfrac{BD}{DC}=\dfrac{AB}{AC}=\dfrac{12}{16}= \dfrac{3}{4}$(T/C pgiác)
mà BD+DC=BC=20\Rightarrow BD=$\dfrac{60}{7}$
\Rightarrow HD=BD-BH=$\dfrac{48}{35}$
 
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