Đáp án:
Ta đo được
$\begin{array}{l}
DB = 4,18\left( {cm} \right)\\
DC = 8,36\left( {cm} \right)\\
\Rightarrow \dfrac{{AB}}{{AC}} = \dfrac{3}{6} = \dfrac{1}{2}\\
\dfrac{{DB}}{{DC}} = \dfrac{{4,18}}{{8,36}} = \dfrac{1}{2}\\
\Rightarrow \dfrac{{AB}}{{AC}} = \dfrac{{DB}}{{DC}}
\end{array}$