解法一：所求体积=∫[π(2x-x²)-πx²]dx
=2π∫(x-x²)dx
=2π(1/2-1/3)
=π/3；
解法二：所求体积=∫[2πy*y-2πy*(1-√(1-y²))]dy
=2π∫[y²-y+y√(1-y²))]dy
=2π(1/3-1/2+1/3)
=π/3.