Răspuns :
[tex]\it BC = AD=5\ cm\ (laturi\ opuse)\\ \\ \Delta ABC-\ dreptunghic,\ \hat B=90^o,\ \hat A=30^o\ \stackrel{T\angle30^o}{\Longrightarrow}\ \ AC=2\cdot BC=2\cdot5=10\ cm\\ \\ ABCD\ -\ dreptunghi\ \Rightarrow BD=AC=10\ cm[/tex]
[tex]\it BC = AD=5\ cm\ (laturi\ opuse)\\ \\ \Delta ABC-\ dreptunghic,\ \hat B=90^o,\ \hat A=30^o\ \stackrel{T\angle30^o}{\Longrightarrow}\ \ AC=2\cdot BC=2\cdot5=10\ cm\\ \\ ABCD\ -\ dreptunghi\ \Rightarrow BD=AC=10\ cm[/tex]