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Math Help - I figured out the half angle just need help with the math

  1. #1
    Member M670's Avatar
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    I figured out the half angle just need help with the math

    Given and is in quadrant III, find the exact value of .
    Note: You are not allowed to use decimals in your answer. =
    \cos(\frac{\alpha}{2})=-\sqrt\frac{1+-(\frac{4}{5})}{2}
    I need help with the math after this??
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  2. #2
    Senior Member jakncoke's Avatar
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    Re: I figured out the half angle just need help with the math

     1 - \frac{4}{5} = \frac{5 - 4}{5}  = \frac{1}{5} bring the 5 down. You get  -\sqrt{\frac{1}{2 * 5 }}
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  3. #3
    Member M670's Avatar
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    Re: I figured out the half angle just need help with the math

    That worked perfectly
    -\sqrt\frac{1}{10} is just what I needed
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