Explicație pas cu pas:
[tex]Aria_{4} = {\ell_{4}}^{2} \iff {\ell_{4}}^{2} = 36 \ {cm}^{2} \implies \ell_{4} = 6 \ cm \\ [/tex]
[tex]P_{4} = 4 \cdot \ell_{4} = 4 \cdot 6 = 24 \ cm \\ [/tex]
[tex]P_{3} = P_{4} \implies P_{3} = 24 \ cm \\ [/tex]
[tex]P_{3} = 3 \cdot \ell_{3} \iff 3 \cdot \ell_{3} = 24 \implies \bf \ell_{3} = 8 \ cm \\ [/tex]
[tex]\ell_{3} = R \sqrt{3} \iff R = \frac{\ell_{3} \sqrt{3} }{3} \\ \implies \bf R = \frac{8 \sqrt{3} }{3} \: cm[/tex]
