x^2 + y^2 = 2y,x^2 + (y - 1)^2 = 1
x = rcosθ,y = rsinθ
r = 2sinθ
∫∫ √(x² + y²) dxdy
= ∫(0→π) ∫(0→2sinθ) r² drdθ
= ∫(0→π) r³/3 |(0,2sinθ) dθ
= ∫(0→π) (8/3)sin³θ dθ
= ∫(0→π) (8/3)(cos²θ - 1) d(cosθ)
= (8/3)[(1/3)cos³θ - cosθ] |(0,π)
= (8/3)[(1/3)cos³π - cosπ] - (8/3)[(1/3) - 1]
= 32/9
= 3又(5/9)