[tex]\it \left.\begin{aligned} \it OA=OC=6cm \Rightarrow[OA]\equiv[OC]\\ \\ \it \widehat{DOA}\equiv\widehat{COB}\ (opuse\ la\ v\hat arf)\ \ \ \ \end{aligned}\right\} \stackrel{C.U.}{\Longrightarrow} \Delta AOD\equiv \Delta COB\\ \\ \\ \Delta AOD\equiv \Delta COB \Rightarrow\begin{cases} \it [OD]\equiv [OB]\\ \\ [AD] \equiv [BC]\end{cases}[/tex]
În două triunghiuri congruente, la unghiuri congruente se opun laturi congruente.
