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## Homework Statement

A spherical shell of radius [itex]R[/itex] carries surface charge density [itex]\sigma=k \cos \theta[/itex]. Whats the dipole moment of this distribution?

## Homework Equations

The dipole moment is calculated as [itex]\bf{p} = \int \bf{r}' \sigma (\bf{r}') d\bf{a}'[/itex] (Griffiths, Eq. 3.98).

## The Attempt at a Solution

The Ansatz is supposed to be [itex]\int (R \cos \theta) (k\cos \theta) R^2 \sin\theta d\phi d\theta[/itex]. I get every factor except for (R \cos \theta). Where does that come from?

Thanks for any help.