Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

How do you do this weird integral?

  1. Mar 22, 2009 #1

    I came upon this strange integral:

    [tex]\int \frac{f(x,y)}{x}dx[/tex]

    How would one attempt to solve this? Would integration by parts do?
  2. jcsd
  3. Mar 22, 2009 #2
    What is f(x,y) ? Unless you have a more specific formula, there is not much you can do to compute or simplify the integral.
  4. Mar 22, 2009 #3
    Like yyat said, unless we have more info about f(x,y) we can't really say anything about it.
  5. Mar 22, 2009 #4
    Are yoiu going to tell us what f(x,y) is?
  6. Mar 22, 2009 #5
    If x and y are independent variables, then just integrate normally with respect to x and treat y as a constant.

    If y = g(x), then plug in.

    If y is an implict function of x, some method of integration might make your life easier. This would be a lot easier to do on a case by case basis.
  7. Mar 22, 2009 #6
    or if: f(x,y)=0 the integral is zero(0) or if

    f(x,y)=1=> integral is ln|x|

    (just messing around)!
  8. Mar 22, 2009 #7
    ... just for clarification, I was being serious. I think I just about listed all the cases. Did I miss one?
  9. Mar 22, 2009 #8
    Excuse post #6. If you interpreted it as a joke to your post, it was not meant to be so.

    I think you mentioned about all possible cases. The OP, might also consider differetiating under the integral sign as well, if applicable. But since there are no info whatsoever about the nature of f(x,y), then god help us.
  10. Mar 23, 2009 #9
    No offense taken!

    I agree that the problem is sort of vague. I mean, I could ask you how you solve the equation

    f(x) = 0.

    It... uh... sort of depends on, well, what f(x) is.
  11. Mar 28, 2009 #10
    Well, I meant f(x,y) to just be an arbitrary function of x and y. My question was meant to find out what the general form of the integral would be. Sorry for the confusion!
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook