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!

Integral problem

  1. Mar 21, 2007 #1

    dnt

    User Avatar

    1. The problem statement, all variables and given/known data

    how do you integrate (xcox)dx

    2. Relevant equations

    n/a

    3. The attempt at a solution

    ive gone through so many ways that ive learned how to integrate problems and i cannot figure this one out. can someone just give me a hint on how to start it? thanks. (i have a feeling this is easy and im overlooking a really basic way of doing it)
     
  2. jcsd
  3. Mar 21, 2007 #2

    VietDao29

    User Avatar
    Homework Helper

    When seeing a product of a polynomial and ex, or some kind of trigonometry functions. One should think about Integrate by Parts.
    By letting u = the polynomial, in this case u = x.
    And dv = the rest.
    By the way, is your problem:
    [tex]\int x \cos x dx \quad \mbox{or} \quad \int x \cot x dx[/tex]?
    Can you go from here? :)
     
  4. Mar 21, 2007 #3
    Integration by parts.
     
  5. Mar 21, 2007 #4
    I do not know if this mnemonic is taught everywhere, but when I was in school learning integration by parts, we were asked to remember ILATE, without justification, when deciding which part is to be u and which is to be dv. Of course, this rule need not work every time.

    Inverse(Trigonometric)-Logarithmic-Algebraic-Trigonometric-Exponential.

    The one that comes before the other will be u.
     
  6. Mar 21, 2007 #5

    dnt

    User Avatar

    thanks. i knew it was easier than i thought.

    and btw it was cos (forgot the s)
     
  7. Mar 21, 2007 #6

    VietDao29

    User Avatar
    Homework Helper

    Well, yes, some of the textbooks here do mention it. However, the are very rare, I think.
    Btw, I don't know what it's called in English. Since, I am not a native-English speaker. Still have to learn a lot. :blushing:
    So yeah, thanks for the info. :)
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?



Similar Discussions: Integral problem
  1. Integration problem (Replies: 4)

  2. Integral Problem (Replies: 31)

  3. Integration problem (Replies: 9)

  4. Integration Problem (Replies: 7)

Loading...