1. Not finding help here? Sign up for a free 30min tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Integration math question

  1. May 26, 2008 #1
    If we were to integrate 1/x by parts using u = 1/x and dv = 1dx, then it would end up as:
    Int(dx/x) = 1 + Int(dx/x), ending up with 1 = 0. Why was there a discrepancy in the integration?
    --Int() refers to integral
  2. jcsd
  3. May 26, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper

    You're missing an integration constant.
  4. May 26, 2008 #3


    User Avatar

    [tex]\int\frac{1}{x}dx=uv -\int vdu= \frac{x+c}{x} - \int \frac{-(x+c)}{x^{2}}dx = etc...[/tex]

    Please tell me if I am wrong.

    Regardless, you are looking for the result to be ln|x|+c.
  5. May 26, 2008 #4


    User Avatar
    Homework Helper

    I don't think there should be a '+ c' in this intermediate step. Anyway, integrating
    1/x gives ln(x) + c by definition. Some books actually define ln(x) to be the anti-derivative of that.
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Integration math question
  1. Maths question (Replies: 1)

  2. Integration Proof math (Replies: 3)