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What's the indefinite integral?

  1. Aug 19, 2008 #1
    of sin pi x dx

    i thought it would be - cos pi x dx but i think it might be (1/pi) -cos pi x dx
  2. jcsd
  3. Aug 19, 2008 #2
    [tex] \int \sin (\pi x)\, \mathrm{d}x =\frac{1}{\pi} \int \sin (\pi x) \, \mathrm{d} (\pi x)[/tex]

    Does this help?
  4. Aug 19, 2008 #3
    yea a lot thanks, i guessed right but i didn't know if i was right
  5. Aug 19, 2008 #4
    just wondering why is it 1/pi, i'm not even sure why
  6. Aug 19, 2008 #5


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    What is the derivative of cos(pi x)?
  7. Aug 19, 2008 #6
    it's - sin (pi x)
  8. Aug 19, 2008 #7
    To integrate [tex] sin( \pi x) dx [/tex] consider doing a substitution of [tex] u = \pi x [/tex] then substitute in the appropriate expression of dx in terms of du.
  9. Aug 20, 2008 #8


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    Well, there is you problem then: it isn't. Use the chain rule.
    Last edited by a moderator: Aug 20, 2008
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