# Simple question about direct integration

1. Jun 18, 2006

### Tuneman

if I have a equation like this

I know I can integrate so that

but this does not make sense to me because I could think of many U's that if you were to take the derivitive with respect to the squiggly varibale, still includes both variables

2. Jun 18, 2006

### Hurkyl

Staff Emeritus
If the derivative with respect to xi includes both variables, then how does it look when you differentiate with respect to both xi and to eta?

3. Jun 18, 2006

### Tuneman

Last edited: Jun 18, 2006