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Thread: Plz solve integration problem

  1. #1

    Thread Starter
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    Plz solve integration problem

    i am integrating it by two methods

    a=integration{(sin(x).cos(x).dx}

    i).first using by parts
    a=int{sin(x).cos(x)}
    I II
    a=[sin(x).sin(x)] - int{cos(x).sin(x)}]
    a=(sin(x))^2 - a
    2a=(sin(x)^2)
    a=(sin(x)^2)/2
    put x=30
    a=.125 --------------------------------------------------------(1)

    ii).by using trigonometry relation
    a=int{sin(x).cos(x)}
    a=(1/2).int{2.sin(x).cos(x)}
    a=(1/2)int{sin(2x)}
    a=(1/2).(-cos(2x))/2

    put x=30
    a= -0.125 ----------------------------------------------------(2)
    how is it possible

    help!!!!!

  2. #2
    Addicted Member Glaysher's Avatar
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    Jul 2006
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    Re: Plz solve integration problem

    Corrections made

    Quote Originally Posted by monu2010
    i am integrating it by two methods

    a=integration{(sin(x).cos(x).dx}

    i).first using by parts
    a=int{sin(x).cos(x)}
    I II
    u = sin (x) and v' = cos(x)
    u' = cos(x) and v = - sin(x)

    a= - [sin(x).sin(x)] + int{cos(x).sin(x)}]
    a=-(sin(x))^2 + a

    Not useful

    ii).by using trigonometry relation
    a=int{sin(x).cos(x)}
    a=(1/2).int{2.sin(x).cos(x)}
    a=(1/2)int{sin(2x)}
    a=(1/2).(-cos(2x))/2

    put x=30
    a= -0.125 ----------------------------------------------------(2)
    how is it possible

    Correct

    help!!!!!
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  3. #3
    Member
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    Jul 2006
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    49

    Re: Plz solve integration problem

    Yes, unfortunately you missed a negative, so your first solution isn't quite right.

    Glaysher is on fire today!!

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