## anonymous 5 years ago The volume of a solid sphere of radius r is given by the equation V=4/3TTr^3. Derive this equation by using either the disk or shell method for finding the volume of a solid of revolution.

1. anonymous

I assume TT is supposed to be $$\pi$$. How did you want to set this up?

2. anonymous

correct I didn't know how to make the pi symbol.

3. anonymous

Using Disk method: $\pi \int\limits_{-r}^{r} (r^2 - x^2)^2dx = \int\limits_{-r}^{r} (r^2-x^2)$ $= r^2x-x^3/3$ from -r to r $\pi (2r^3/3 - (-2r^3/3)) = 4\pi r^2/3$

4. anonymous

yay, another student given the answer with no effort or thinking required. GJ!

5. anonymous

Btw, if you just want answers you can probably google it faster than we can type it for you.. see: http://en.wikipedia.org/wiki/Sphere#Volume_of_a_sphere

6. anonymous

If you want to actually understand what's going on you should probably elaborate more on what part is confusing you, etc.

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