Lc=2pi×r
9pi=2×3,14×r
9×3,14=6,28r
28,26=6,28r
r=4,5
Acerc= pi×r²
8 pi=pi×r²
8×3,14=3,14×r²
=>
r²=(8×3,14):3,14
r²=25,12:3,14
r²=8
[tex]r = \sqrt{8} \\ r = 2 \sqrt{2} [/tex]
