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Math Help - Small integral problem (one step)

  1. #1
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    Small integral problem (one step)

    I'm not great when it comes to integrals.

    I have

    Sin^2(2x)

    I know Sin(x) goes to -Cos(x), and Sin(2x) would go to -Cos(2x)(2), right?

    I just don't know how to approach Sin^2(2x)

    thanks
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  2. #2
    MHF Contributor red_dog's Avatar
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    \sin^22x=\frac{1-\cos 4x}{2}
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  3. #3
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    I have a follow up question.

    Doing a seperate part of the same question, I have xsin(2x)

    Would this be [(x^2)(-cos(2x)(2)]/2 ?
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  4. #4
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    Quote Originally Posted by JTG2003 View Post
    I have a follow up question.

    Doing a seperate part of the same question, I have xsin(2x)

    Would this be [(x^2)(-cos(2x)(2)]/2 ?
    no ... \int x \sin(2x) \, dx has to be done by parts.
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  5. #5
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    Quote Originally Posted by skeeter View Post
    no ... \int x \sin(2x) \, dx has to be done by parts.

    Done by parts? Sorry, I don't know what you mean by that ...
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  6. #6
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    Quote Originally Posted by JTG2003 View Post
    Done by parts? Sorry, I don't know what you mean by that ...
    Integration by parts.

    If you don't know this technique then I don't know why you'd be asked to solve this integral (unless you were previously asked to find the derivative of x \cos (2x)).
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  7. #7
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    Sorry, I'm taking calc + calc II as summer classes.. it's all going very fast. I'm having a hard time keeping up.
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  8. #8
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    Quote Originally Posted by JTG2003 View Post
    Sorry, I'm taking calc + calc II as summer classes.. it's all going very fast. I'm having a hard time keeping up.
    recommend you visit this site ... it has much help to offer you in your current academic predicament

    Pauls Online Notes : Calculus II - Integration by Parts
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