图形绕y轴旋转所成的旋转体的体积表达式为∫π*x^2dx体积=∫π*(y^2)^2dx-∫π*ydx ; 积分下限是0，上限是1 =∫π*ydx-∫πy^4dx =π*(1/2*y^2-1/5y^4) =π*(1/2-1/5)=1/3π
