>>856
V=∫_{(x-1)^2+y^2≦1} (1/4)(x^2+y^2)dxdy
を極座標変換
V=∫[-π/2,π/2]dθ∫[0,2cosθ](1/4)r^3d
=∫[-π/2,π/2](cosθ)^4dθ
=(3/8)π