[tex]\it AM - median\breve a \Rightarrow AM = \dfrac{BC}{2} \Rightarrow AM=BM \Rightarrow \Delta ABM-isoscel\ \ \ \ \ (1)\\ \\ \\ Din\ \Delta ADM \Rightarrow \widehat{DMA}=60^o\ \ \ \ \ \ (2)\\ \\ \\ (1),\ (2) \Rightarrow \Delta ABM-echilateral\\ \\ \\ Din\ \Delta ADM,\ cu\ Th.\ \angle30^o \Rightarrow AM=2\cdot DM=2\cdot3=6cm\\ \\ \\ BC = 2\cdot AM=2\cdot6=12\ cm[/tex]
