Răspuns :
[tex]\it T.\measuredangle\ 30^o\ pentru\ \Delta DAB \Rightarrow BD=\dfrac{AB}{2}=\dfrac{4}{2}=2\ cm\\ \\ \\ T.\ catetei\ \hat\imath n\ \Delta ABC \Rightarrow AB^2=BD\cdot BC \Rightarrow BC=\dfrac{AB^2}{BD}=\dfrac{4^2}{2}=\dfrac{16}{2}=8\ cm\\ \\ \\ CD=BC-BD=8-2=6\ cm\\ \\ \\ \dfrac{CD}{BD}=\dfrac{6}{2}=3[/tex]