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Indefinite Intergrals

  1. Feb 3, 2010 #1

    DMT

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    Hey, I just need you guys to help verify that I got the correct answers on some of the even integration problems in my book. If one of them is incorrect, I'll post my work and hopefully can find out where I went wrong. Thanks!

    1. [tex]\int[/tex] xcos(x[tex]^{2}[/tex])dx = [tex]\frac{1}{2}[/tex] sin(x[tex]^{2}[/tex]) +C

    2. [tex]\int[/tex] x[tex]^{2}[/tex]cos(x)dx = x[tex]^{2}[/tex]sinx + 2xcosx - 2sinx + C

    3. [tex]\int[/tex] x[tex]^{2}[/tex]e[tex]^{-x}[/tex]dx = -e[tex]^{-x}[/tex](x[tex]^{2}[/tex] +2x + 2) + C

    4. [tex]\int[/tex] e[tex]^{x}[/tex]sinxdx = [tex]\frac{1}{2}[/tex](-e[tex]^{x}[/tex]cosx + e[tex]^{x}[/tex]sinx) + C
     
  2. jcsd
  3. Feb 3, 2010 #2

    Dick

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    Hah! They are all right. Which probably suggests you are pretty good at what you are doing and don't really have a real "question". I'm not sure just checking homework answers is really what we're about here.
     
  4. Feb 3, 2010 #3

    DMT

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    Ok, sorry! I just wanted to make sure they were correct before I turned it in so my instructor wouldn't take off points. I'll keep my posts to HW help from now on. Though, if one of the answers ended up being incorrect, the post would have turned into a homework help post right away ;)
     
  5. Feb 3, 2010 #4
    http://en.wikipedia.org/wiki/Dimethyltryptamine" [Broken]??
     
    Last edited by a moderator: May 4, 2017
  6. Feb 3, 2010 #5

    DMT

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    fun stuff!
     
    Last edited by a moderator: May 4, 2017
  7. Feb 3, 2010 #6

    Dick

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    Oh, that's ok. But there is no reason to post to HW help just to check answers to avoid point reductions. I think you should be genuinely confused before posting. Just my opinion.
     
  8. Feb 4, 2010 #7

    vela

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    You can use the online integrator provided by Wolfram to check your answers.

    http://integrals.wolfram.com/index.jsp

    Also, you could just differentiate your result and see if you recover the integrand.
     
  9. Feb 4, 2010 #8

    DMT

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    Wow! That is an amazing tool. Thanks for the link!
     
  10. Feb 4, 2010 #9

    Mark44

    Staff: Mentor

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