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What is the integral 1/x log(x) or lnx?

  1. Oct 26, 2011 #1
    1. The problem statement, all variables and given/known data
    I know it is supposed to be lnx however I find something peculiar. When I integrate it in wolfram alpha they give the integral as log(x). What the heck is going on here!?!


    2. Relevant equations



    3. The attempt at a solution
     
  2. jcsd
  3. Oct 26, 2011 #2
    If you check closer on Wolfram, by log(x) they mean the natural logarithm.
     
  4. Oct 26, 2011 #3
    ok thanks, When looking at more complex solutions sometimes there are many logx's how am I supposed to know which one is logx and which one is not really logx?
     
  5. Oct 26, 2011 #4
    They will usually define what they use. As a rule of thumb, I find that they always tend to use the natural log, but it could happen that they don't. Just pay attention to the bottom of the equation box thingy. :smile:
     
  6. Oct 26, 2011 #5
    the derivative of ln(x) is "one over the thing inside, times the derivative of the thing inside" -- my calc professor

    so, y = ln (x); y' = 1/x * 1 = 1/x

    i'm not sure if this helps or not... you are asking for y given y' = 1/x ?
     
  7. Oct 26, 2011 #6
    ok thanks guyz I precciate ya!
     
  8. Oct 26, 2011 #7

    dextercioby

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    It's simple. The 'Mathematica' software developed by Wolfram himself or his company has the natural logarithm (aka neperian logarithm) denoted as LOG, instead of the widely used LN which is derived from <natural logarithm> spelled in Latin. Most people use LOG for the logarithm in other base than Euler's number 'e'.
     
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