# Ln x dx

1. Jan 4, 2004

### PrudensOptimus

Integrat Ln[x]dx!!!!

2. Jan 4, 2004

### Lonewolf

Consider it as 1*ln(x) and use parts.

3. Jan 4, 2004

### Tron3k

If you don't feel like doing it, you can always use:

The Integrator

It gives the answer:

$$-x + x \ln x$$

4. Jan 5, 2004

### himanshu121

Is [x] greatest integer function??

5. Jan 5, 2004

### Lonewolf

Hmm, didn't consider that. I'm not sure there'd be a closed form expression for $\int ln[x] dx$
where $[x]$ is the next greatest integer function. It'd be easy enough to get a numerical answer if the interval was specified though.

Last edited: Jan 5, 2004
6. Jan 5, 2004

### sam2

You could break the integral into a summation. [x] is constant between intervals of integers, so you end up with a sum of trivial integrals.

I think this is what Lonewolf is proposing (please excuse my ignorance!)

Regards,
Sam