Respostas

2014-03-24T14:06:52-03:00
180° = π 
36° = x

180x = 36π 

 x = 36π /180

x = 18π /90

x =  9π /45

x = 3π /15

x = π / 5

agora:

π / 5 = 10π m²
2π     = π . r²

π      =  10
10π =    r²

1    =   10
10  =   r²

r² = 100

r = 10 m