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Homework Help: Need help with an integration

  1. Jan 10, 2009 #1
    I am trying to solve this integral. Any help would be great.

    I 5/(3+4sinx)

    I tried suddinb t=tan x/2 but it gives me a result of:

    =5 I (1+x^2)/(3+11x)

    I am not sure what to do with this or if this is the right emthod any help would be great.

    Thanks

    Using I for integration sign.
     
  2. jcsd
  3. Jan 10, 2009 #2

    tiny-tim

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    Hi CaspianTiger! :smile:

    (have an integral: ∫ :wink:)
    Are you sure (1+t2)dt/(3+11t) is right?

    Anyway, then you use long division and/or partial fractions. :wink:
     
  4. Jan 10, 2009 #3
    Hmm.... I am not sure if this is right. I am just following a method from a book. But it doesn't have an example like this one.

    Usually with these problems from the book, you have to use ∫1/x^2+or-a^2

    To get the result (1+t2)dt/(3+11t)

    I made 3+4sinx = 3+ 8t/(1+t^2)

    Then i add them and put them back into the integral. Usually i have a t^2 in the denominator. SO i am confused by this one. The wolf integrator has an insane answer though.
     
  5. Jan 11, 2009 #4

    tiny-tim

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    (just got up :zzz:)

    ah, but 3+ 8t/(1+t2) = (3+ 8t + 3t2)/(1+t2) :wink:
     
  6. Jan 11, 2009 #5
    Greetings,
    I'm not so good in integrations, but I tryed to solve it with Mathematica, and I got this answer

    (5 I (121 x^2-66 x+260 log(11 x+3)-27))/2662

    Hopefully it can help.
     
  7. Jan 11, 2009 #6
    What a stupid mistake.

    Thanks.
     
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