Integral of e^x/x

  • #1
First of all, I want to clarify that i know the answer is Ei(x). I have found a way to calculate this integral but the result is definetely wrong Anyway, have a look and tell me where is my mistake
http://docs.google.com/View?id=dd4jpgg_1g8ztn3g5 [Broken]
 
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Answers and Replies

  • #2
HallsofIvy
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Many people (and I am one when I am not using my home computer where I know how strong my virus- protection is) will not open "word" files. They are notorious for harboring viruses.
 
  • #3
Many people (and I am one when I am not using my home computer where I know how strong my virus- protection is) will not open "word" files. They are notorious for harboring viruses.

Really ? Didn't know that... Well, i can garentee it contains only calculus. Apart from that why why would someone upload a doc file with viruses to physics forums?? I hope i learn "latex" soon so i won't need these word documents
 
  • #4
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Really ? Didn't know that... Well, i can garentee it contains only calculus. Apart from that why why would someone upload a doc file with viruses to physics forums??
For at least two reasons: they knew that the file contained a virus and wanted to spread it; they didn't know the file contained a virus. For a person intent on spreading a computer virus, there is nothing sacrosanct about physicsforums.
 
  • #5
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How about googledocs???
 
  • #6
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It seems that you have missed 1/x in step 2. The final answer you got is just e^x +
c. How it can be? Can you check step no. 2?

Regarding MS word one can disable macros and defend from viruses. For me it worked!!
 
  • #7
Here is the google docs equation
http://docs.google.com/View?id=dd4jpgg_1g8ztn3g5 [Broken]
 
Last edited by a moderator:
  • #8
It seems that you have missed 1/x in step 2. The final answer you got is just e^x +
c. How it can be? Can you check step no. 2?

Regarding MS word one can disable macros and defend from viruses. For me it worked!!

I know it can't be e^x+c ... I didn't miss it!! Check the google document du=1/x dx
 
  • #9
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e^lnx = x is true only if x>0 right? I tried conventional method to solve this integral and i got different answer. I have to check my answer.
 
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  • #10
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It's the 5th line. [tex]u[/tex] is independent variable here, so [tex]u'=1[/tex].
 
  • #12
e^lnx = x is true only if x>0 right? I tried conventional method to solve this integral and i got different answer. I have to check my answer.

Of course. There can't be a ln(-|x|)
 
  • #13
It's the 5th line. [tex]u[/tex] is independent variable here, so [tex]u'=1[/tex].

Really? I thought that since u=g(x) u'=g'(x)=lnx'=1/x
 
  • #14
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Whatever way I try it is bouncing back to beginning.
Finally wikipedia page gave me the answer.
http://en.wikipedia.org/wiki/Exponential_integral
Gave you WHAT answer? That article doesn't explain where the error is...

It's the 5th line. [tex]u[/tex] is independent variable here, so [tex]u'=1[/tex].
Yes, you are having problems with the chain rule. If v = e^u, then dv/du = e^u, and dv = (e^u)du, which doesn't help solve the integral.
If you wanted to take dv/dx, then that would equal (dv/du)*(du/dx), but that's not what you're doing... (and won't help any)
 
  • #15
Try this one:
[tex]e^x\sum_{i=1}^\infty(i-1)!x^{-i}[/tex]
 
  • #16
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[tex] e^{elnx} = e^x[/tex] ?
 

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