i have a question that asks for the volume of the sphere using "Volume of Solids of Revolution" i know that the volume formula of a sphere is 4/3*pi*r^3 but how do i get to that because when i integrate the area, i come up with 1/3*pi*r^3. i just need to know how to go from the integral of pi*r^2 to 4/3*pi*r^3.

thanks in advance