# Vector integration

## Homework Statement

Prove $$\int\int_{S}r \times dS=0$$
for any closed surface S.

## The Attempt at a Solution

i used divergence theorem but i didn't make it...

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gabbagabbahey
Homework Helper
Gold Member
i used divergence theorem but i didn't make it...
Well, how far did you make it with that? Show us what you've got and we'll be better able to help you.

the value of r= x^2+y^2+z^2

gabbagabbahey
Homework Helper
Gold Member
the value of r= x^2+y^2+z^2
First,

$$r=||\textbf{r}||=\sqrt{x^2+y^2+z^2}\neq x^2+y^2+z^2[/itex]. Second, is this the entirety of your attempt at the problem? What does this have to do with computing the integral [tex]\int\int_{\mathcal{S}}\textbf{r}\times d\textbf{S}$$

??

i dont know sir...

gabbagabbahey
Homework Helper
Gold Member
Try applying the divergence theorem to the vector field $\textbf{c}\times\textbf{r}$, where $\textbf{c}$ is any constant (position independent) vector.... What does that give you?

thank you sir...
but can i have the complete solution of it sir..
thank you

gabbagabbahey
Homework Helper
Gold Member
but can i have the complete solution of it sir..
No. We do not provide complete solutions here. It is unethical and it doesn't really help you learn any problem solving skills.

You need to make some effort and show your work in order to receive further help.