# How to prove volume and surface area of sphere [duplicate]

Possible Duplicate:
Why is the volume of a sphere $\frac{4}{3}\pi r^3$?

We know that the surface area of a sphere is $4\pi r^2$ where $r$ is the radius of the sphere, and the volume is $\frac{4}{3}r^3$.

How does one prove these formula?

-

## marked as duplicate by Hans Lundmark, Thomas, rschwieb, Ross Millikan, no identityOct 21 '12 at 16:56

... and see also math.stackexchange.com/questions/625/… –  Hans Lundmark Oct 21 '12 at 15:16

For the area, use the equation of a circle of radius $r$, $x^2+y^2=r^2$, to find the area between two curves.
For the volume, view the sphere of radius $r$ as a solid of revolution of the function $y=\sqrt{r^2-x^2}$.