where $ is the integral symbol , how can i get a general solution to

the indefinite integral $ dx / ln(x) .

problem relates to the primes.

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- Apr 29th 2008, 02:51 PMDemusGauss integral
where $ is the integral symbol , how can i get a general solution to

the indefinite integral $ dx / ln(x) .

problem relates to the primes. - Apr 29th 2008, 02:58 PMMathstud28
- Apr 30th 2008, 06:49 AMCaptainBlack
- Apr 30th 2008, 09:27 AMDemusintegrals
thanks M28 , your reply was helpful as it does form part of a solution

as far as mathcad is concerned .there does seem to be more to it which i do

not understand yet , involving Ei , the exponential integral .I wonder if captain black can explain this ? - Apr 30th 2008, 11:40 AMCaptainBlack
Sloppy work on my part I of course meant the logarithmic integral:

or the offset logarithmic integral (to aviod the singularity at 1):

But also the exponential integral:

Now this has not been as careful as I would like so still probably needs checking some more.

See the Wikipedia artice on the logarithmic integral for more information.

RonL - Apr 30th 2008, 01:12 PMDemusLi
I would like to show symbols . As i am very newbie , i'm in need of tutorials so as to better illustrate my questions .

I came across the integral when reading about Guass . It looked harmless untill i tried to integrate . Eventually i gave up and solved it symbolic using mathcad .Then i realised i was in over my head with the Ei.

My next quest is to understand how Ei is derived .

many thanks . - Apr 30th 2008, 01:19 PMMathstud28
Exponential Integral -- from Wolfram MathWorld

It isnt derived it comes from the incapability to get a closed solution to - Apr 30th 2008, 03:12 PMDemusEi(x)
I expanded the integrand several terms of \int\frac{e^{x}}{x}dx , and i think i can see why ln (x) is in Ei(x) . Thanks .

- May 1st 2008, 12:32 PMCaptainBlack
We use LaTeX for mathematical typesetting here. You will find the tutorial here

RonL - May 1st 2008, 02:44 PMDemus
Testing 1 2 3 .

where is Euler's constant .

Thanks for your help guys .