Znáš poloměr kružnice \( \:k \), jak velký bude průměr kružnice?
\( \large r = xcm \)
\( \large d = x \cdot r = x \cdot x = x^2cm \)
\( \large d = r + x = 2xcm \)
\( \large d = 2 \cdot r = 2 \cdot x = 2xcm \)
\( \large d = 3 \cdot r = 3 \cdot x = 3xcm \)
