>>277
y=√(r^2-x^2)
V=2∫_[d/2~r] πy^2 dx=2π∫_[d/2~r] (r^2-x^2)dx=2π( r^2(r-d/2)-[x^3/3]_[d/2~r] )
=2π(2r^3/3-dr^2/2+d^3/24)