# How can you prof?

1. Sep 30, 2007

### yaho8888

1. The problem statement, all variables and given/known data

$$\int \pi (\frac{x}{3})^2 dx$$

how can you tell whather this equation is for hemisphere or cone.

no idea how to start.

2. Sep 30, 2007

### Staff: Mentor

First, that is not an equation, it's an indefinite integral. Second, it is a fairly easy to solve integral. Third, it would appear to have nothing to do with the 3-dimensional mathematical description of either a hemisphere or a cone.

Could you please rephrase the question?

3. Sep 30, 2007

### Hurkyl

Staff Emeritus
It's not even an equation...

4. Sep 30, 2007

### HallsofIvy

Staff Emeritus
The "equation" isn't for either one! If the question is really what you say , it has nothing to do with a cone or a hemistpher. It's an integral! Knowing that the integral of x2 is (1/3)x3 should make it easy!

5. Sep 30, 2007

### yaho8888

it is an intergral for finding the volume of a cone or a hemistpher.
forgot from 0 to 12.

6. Oct 1, 2007

### yaho8888

any one knows

7. Oct 1, 2007

### HallsofIvy

Staff Emeritus
Any one knows WHAT? What question are you asking? An integral is an integral. You can get exactly the same integral for different applications.

Typically to find volume you have to integrate some kind of area. Looks to me like (x/3) is some kind of radius (so that $pi (x/3)^2$ is the area of a circle). In other words, it looks like you are doing a volume of rotation. But then the radius is a LINEAR function of x- the part that being rotated is a straight line: okay is that a cone or a sphere?