Violympic toan 8

T

thienbinhgirl

..........................................................................................17,5............................................................................................................................................................................................
 
C

chonhoi110

Có $AD$ là phân giác $\widehat{A}$

$\rightarrow \dfrac{AB}{AC}=\dfrac{BD}{CD}\rightarrow \dfrac{AB}{BD}=\dfrac{AC}{CD}=\dfrac{AB+AC}{BD+DC}=\dfrac{12+20}{28}=\dfrac{8}{7}$

$\rightarrow CD=\dfrac {7.20}{8}=17,5$
 
H

huynhbachkhoa23

Ráp luôn công thức vào:
$CD=\frac{AC.BC}{AB+AC}=17.5$
 
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