[tex]\Delta ABC-triunghi \\\\AB=2 \ \ \to AB^2=4 \\\\ AC=4 \ \ \to AC^2=16 \\\\BC=2\sqrt{5} \ \ \to BC^2=20 \\\\\ 4+16=20 \\ AB^2+AC^2=BC^2 \\\\ \Longrightarrow (R.T.P.) \ \ \ \Delta ABC- triunghi \ dreptunghic \\\\\\ \hbox{R.T.P. - reciproca teoremei lui Pitagora}[/tex]
