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 by parts

  1. May 10, 2007 #1
    intergrate (ln(x))^2

    so i set u=(lnx)^2...which makes du=2lnx(1/x)

    then i set dv=dx...which makes v=x

    according to the formula for integration by parts i have

    x(lnx)^2- integral x(2lnx)(1/x)
    simplifying it i get x(ln)^2-2intergral lnx

    and here is where i am stuck....what i the integral of lnx?
  2. jcsd
  3. May 10, 2007 #2


    User Avatar
    Staff Emeritus
    Science Advisor

    The derivative of (lnx)^2=(2lnx)/x.

    [edit: of course that's you've written... i glanced and say ln(1/x)... sorry :blushing: ]

    A hint for integrating lnx; use parts, taking dv=dx and u=lnx
    Last edited: May 10, 2007
  4. May 10, 2007 #3
    How about integration-by-parts once again? :)
  5. May 10, 2007 #4


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    xln(x) - x looks good from where I'm standing.

    I just wondered "what function gives ln(x) when differentiated? Well ln(x)' = 1/x. So what if I try xln(x)? Now I get ln(x) + 1. So I need to add something to the mix that gives -1 when differentiated." Hence xln(x) - x.
  6. May 10, 2007 #5
    ohhh yes......do integration by part again........

    thank you!
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?

Similar Discussions: Integration by parts
  1. Integration by parts (Replies: 6)

  2. Integration by parts (Replies: 8)

  3. Integration by Parts (Replies: 8)