[tex]\it \mathcal{A} _{cerc} = \pi R^2 \ \ \ \ (1)
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\mathcal{A} _{cerc} = 36\pi \ \ \ \ (2)
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Din\ \ (1), (2) \Longrightarrow \pi R^2 = 36\pi \Longrightarrow R^2 = 36 \Longrightarrow R = 6 cm[/tex]
Aflăm lungimea cercului folosind formula:
[tex]\it L_{cerc} = 2\pi R[/tex]
