# Integration Problem

1. Jan 23, 2008

### Psi-String

Hi! Could someone give me an idea how the following integration be carried out??

$$\int \frac{r dr}{ \left( r^2 + a^2 - 2rau \right)^{3/2}} = \frac{ru - a}{a(1-u^2)\sqrt{r^2 + a^2 - 2rau}}$$

where u and a are constant.

I have encounter such integration several times in electrodynamics.

I can solve it in lengthy way, but can't carry out such compact result as above. Could someone help me?? Thanks a lot!!

2. Jan 23, 2008

### unplebeian

Look up Sadikus textbook. Or David Griffiths. You'll find a good result there.

3. Jan 23, 2008

### Psi-String

well, this is an integration I need to carry out when solving Griffiths' problem. The solution manual only give the result as above, it didn't take out step by step, and I don't think it is that obvious that we can solve it just by one equation XDDDD