# A general integral question

1. Jan 16, 2005

### bomba923

Ok...now how do I know if a certain integral is solv/integrat-able or not???
Just by looking at the inside function, how can I tell if the integral can be solved or not??

2. Jan 17, 2005

### dextercioby

1.Try conventional methods:part integration,substitutions,partial fraction decompositions,residues theorem.

2.If it doesn't work,then search for it in "Gradsteyn & Rythzik".

3.If it's not there,the primitive/anitderivative exists,but it's not expressible through elementary functions.

Daniel.

3. Jan 17, 2005

### Sirus

The Wolfram Integrator can also be helpful as a quick reference technique.

4. Jan 17, 2005

### dextercioby

Trust me,that one is useless for nasty integrals.I tried it for about 3 times over the last month and it wouldn't give me anything... :grumpy:

Daniel.

5. Jan 17, 2005

### Zurtex

Really? Can you give me an example please.

6. Jan 17, 2005

### dextercioby

I tried an integral that comes up in the Laplace Transform of arctangent

$$\int_{0}^{+\infty} e^{-sx}\arctan x dx$$

Of course,i asked for the antidifferential,i thought i could apply the theorem of Leibniz & Newton myself...

Daniel.

7. Jan 17, 2005

### Zurtex

Works fine for me when I enter:

Code (Text):
Exp[-s x] ArcTan[x]

8. Jan 17, 2005

### dextercioby

Thenx,Zurtex,there's no wonder i couldn't do it... :tongue2: I misstyped something... :grumpy:
I like the result,though... :tongue2:

Daniel.

9. Jan 17, 2005

### Zurtex

Yeah I can't help thinking Wolfram are trying to introduce their own brand of maths