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Homework Help: Antiderivative of 1.4x*cos(x^1.9)

  1. Mar 17, 2008 #1
    Question

    f'(x) = 1.4x*cos(x^1.9)
    Find f(x)

    Attempt
    Ok, first of all, I'm really bad at Calculus, so bear with me >__<
    I figured to find the antiderivative of the thing is equivalent to
    [tex]\int\left1.4x*cos\leftx^{1.9}\right\right)dx[/tex]

    I've tried simple substitution (u = x^1.9) and that obviously doesn't work, and I tried integration by parts, but I don't think it's working
    If I had dv = cos(x^1.9)dx
    I'm unsure if I can find v when x is x^1.9

    Help will be appreciated! Thanks!
     
    Last edited: Mar 17, 2008
  2. jcsd
  3. Mar 17, 2008 #2
    Your doing the math lab arn't you? I have the same problem except my f'(x) = 1.7x*sin(x^1.8)
     
  4. Mar 17, 2008 #3
    You have two different Integrals ... which is it?

    [tex]\int1.4x\cos{x^{1.9}}dx[/tex]

    or

    [tex]\int1.4x\cos^{1.9}xdx[/tex]

    Does the power belong to cosine or the variable x?
     
  5. Mar 17, 2008 #4
    Have you tried Taylor expansion? That's all I can think of now.
     
  6. Mar 17, 2008 #5
    If you're doing the mathlab for a UBC math course *cough*, then use the spreadsheet.
     
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