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Math Help - please help ap calc test tomorrow

  1. #1
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    please help ap calc test tomorrow

    is there a formula for integrating fractions??? sorry if this is hard to understand but i need to find the INTEGRAL of x/(2+e^x).
    Last edited by mr fantastic; May 4th 2010 at 04:05 AM.
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  2. #2
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    integrating fractions

    Hello,

    When facing such problems you should realize that:

    \int \frac{x}{2+e^{x}}dx=\int \left(\frac{1}{2+e^{x}}\cdot x \right)dx

    If you define f(x)=\frac{1}{2+e^{x}} and g(x)=x then you have:

    \int f(x)g(x) dx

    From here you can simply apply the rule of integration by parts.
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  3. #3
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    what is the rule of integration by parts??
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  4. #4
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  5. #5
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    That made no sense to me.

    Please show me with my problem
    Last edited by mr fantastic; May 4th 2010 at 04:08 AM. Reason: Merged and edited posts.
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  6. #6
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    I don't think integration by parts should be used here.

    Are you sure this was the question? This integral is rather difficult to evaluate. Cf. Wolfram Alpha
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    Quote Originally Posted by lovek323 View Post
    I don't think integration by parts should be used here.

    Are you sure this was the question? This integral is rather difficult to evaluate. Cf. Wolfram Alpha
    Yes state the exact question you are having problems with.
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  8. #8
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    Yeah, because I was trying to do this by parts. It is not easy by any means.
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  9. #9
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    There's always an integral involving Li(x) on the AP exam, right you guys? The AP board loves those almost as much as Si(x).
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  10. #10
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    Quote Originally Posted by maddas View Post
    There's always an integral involving Li(x) on the AP exam, right you guys? The AP board loves those almost as much as Si(x).
    I never took AP and we didn't learn that in calc 1 or 2. What is Li(x) and Si(x)?
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  11. #11
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    Quote Originally Posted by helpmeee View Post
    is there a formula for integrating fractions??? sorry if this is hard to understand but i need to find the INTEGRAL of x/(2+e^x).
    Are there integral terminals, that is, is it a definite integral?
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  12. #12
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    Quote Originally Posted by helpmeee View Post
    is there a formula for integrating fractions??? sorry if this is hard to understand but i need to find the INTEGRAL of x/(2+e^x).
    no such integration is required on either the AB or BC exam unless it is a definite integral on the calculator part of the exam.
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