x= ρ cos θ
y= ρ sin θ
x^2+y^2= ρ ^2*(cos^2 θ +sin^2 θ )
x^2+y^2=ρ ^2
(x^2+y^2)^2= ρ ^4
Элемент dxdy=ρdρd θ
0 ≤ θ ≤ 2π
0 ≤ ρ ≤ 2
∫∫ _(D)(x^2+y^2)^2dxdy = ∫ ^(2π)_(0)∫^(2)_(0) ρ ^4 *(ρdρd θ)=
= ∫ ^(2π)_(0)d θ ∫ ^(2)_(0) ρ ^5dρ=
=2π*( ρ ^(6)/6)=2π*2^6/6=128π/6= [b]64π/3[/b]