azzurro
π/2*3^2-π/2*1*3 = 6π/2 = 3π
rosa
π/2*3^2-π/2*1,5^2*2 = π/2(9-4,5) = 2,25π
a/r = 3/2,25 = 12/9 = 4/3
A (blu) =pi·R^2/2 - 3·pi·ρ^2/2 = pi·3^2/2 - 3·pi·1^2/2 = 3·pi cm^2
A (rosa) =pi·R^2/2 - 2·pi·r^2/2 = pi·3^2/2 - 2·pi·1.5^2/2 = 2.25·pi cm^2
Α(blu)/Α(rosa) = 3·pi/(2.25·pi) = 4/3
A1=(9pi-3*1pi)/2=3pi A2=(9pi-2*2,25pi)/2=2,25picm2