Răspuns :
lungimea cercului =2πr=18 cm
2πr=18 ⇒r=18:2π⇒
r=9:π=9:3,14=2,866 cm
r=2,866 cm
2πr=18 ⇒r=18:2π⇒
r=9:π=9:3,14=2,866 cm
r=2,866 cm
[tex]L_(cerc)=2\cdot\pi\cdot{R}\\
2\cdot\pi\cdot{R}=18(cm)\;\;\;\pi\approx3,14\\
R\;=\;18\;;\;(2\pi)=18:6,28=1800:628\approx2,87(cm)[/tex]