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Math Help - Find the x

  1. #1
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    Find the x

    can someone please help me to find the x:
    2\cos(2x)-2\sin(x)=0
    another one:

    2\sin(x)+\sin(2x)=0

    Thank you very much
    Last edited by mathwhat; May 21st 2010 at 08:55 AM.
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  2. #2
    Super Member dhiab's Avatar
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  3. #3
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    Thank you very much but i did it exactly like you did and in the book the answers are different...
    for 1:

    \frac{\pi}{6}

    \frac{5}{6}\pi

    and for 2:
    \pi

    2\pi
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  4. #4
    MHF Contributor harish21's Avatar
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    Quote Originally Posted by mathwhat View Post
    Thank you very much but i did it exactly like you did and in the book the answers are different...
    for 1:

    \frac{\pi}{6}

    \frac{5}{6}\pi

    and for 2:
    \pi

    2\pi
    The answers you have stated here are correct for the interval from 0 to 2\pi
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  5. #5
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    Quote Originally Posted by dhiab View Post
    Small error: \cos (2x) = 1 - 2\sin^2 (x) NOT 2\sin^2 (x) - 1. So for #1 you will get pi/6 and 5pi/6 ....
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