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2014-10-15T17:28:17+02:00
7,065 = 3,14  x r x r.
7,065 = 3,14 x r² = 3,14r²
r²= 7,065/ 3,14
r =  racine carré de 7,065/3,14 =1,5 metre
Perimetre = diametre x 3,14 = 1,5+1,5 x 3,14 = 9,42 metres

Sauf erreur.