# Exponential Integral

#### g345

##### New member
I am attempting a math problem but I have hit a wall.

I have to integrate Lpr^-1.exp(-r/r0) with respect to r and show that it converges on Lpr0

What L p are is not important but r is a distance and r0 is a factor a constant that represents an attenuation length scale, deﬁned as the distance at which the reduction would be a factor of e. If that is important.

The hard part to me is integrating r^-1.exp(-r/r0) which turns out to be something called the exponential integral?

Can anyone offer help?

#### Jomo

##### Elite Member
I am attempting a math problem but I have hit a wall.

I have to integrate Lpr^-1.exp(-r/r0) with respect to r and show that it converges on Lpr0

What L p are is not important but r is a distance and r0 is a factor a constant that represents an attenuation length scale, deﬁned as the distance at which the reduction would be a factor of e. If that is important.

The hard part to me is integrating r^-1.exp(-r/r0) which turns out to be something called the exponential integral?

Can anyone offer help?
OK, so you want to integral e-r/r wrt r . So what have you tried? Where are you stuck? On this forum, as stated in the guidelines, we offer help not solutions. Did you try to integrate by parts?

#### Dr.Peterson

##### Elite Member
I am attempting a math problem but I have hit a wall.

I have to integrate Lpr^-1.exp(-r/r0) with respect to r and show that it converges on Lpr0

What L p are is not important but r is a distance and r0 is a factor a constant that represents an attenuation length scale, deﬁned as the distance at which the reduction would be a factor of e. If that is important.

The hard part to me is integrating r^-1.exp(-r/r0) which turns out to be something called the exponential integral?

Can anyone offer help?
You found out that it is called "the exponential integral". Did you try searching for information about it> Try this:

https://en.wikipedia.org/wiki/Exponential_integral

That will tell you what you can't do, and what you can. What is it that you need to do, and why?

#### g345

##### New member
Yes I have searched extensively for the exponential integral extensively, but my math knowledge is not at the level I can easily understand what is being said. I am not even sure I am on the right track. Is it even possible to integrate
Lpr^-1.exp(-r/r0) dr [FONT=Verdana,Arial,Tahoma,Calibri,Geneva,sans-serif]to s[/FONT]
how it converges on Lpr0.

Integrating by parts does not work @Jomo

If Wikipedia or google could give me the help I need then I would not be posting here. I need expert help and I hope somebody can at least get me started.