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Math Help - Sorry, I kinda hav a ton of ?'s, so here's another one... plez and thanks again

  1. #1
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    Sorry, I kinda hav a ton of ?'s, so here's another one... plez and thanks again

    The exact value of sin 22.5 deg. is (sq root of a - (sq.root b)) / c. Find a, b, and c.
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  2. #2
    Senior Member DivideBy0's Avatar
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    Quote Originally Posted by Luckegrl_16 View Post
    The exact value of sin 22.5 deg. is (sq root of a - (sq.root b)) / c. Find a, b, and c.
    Using the half-angle formula:

    \sin{\frac{A}{2}} = \sqrt{\frac{1-\cos{A}}{2}}

    In your case,

    \sin{\frac{45}{2}} = \sqrt{\frac{1-\cos{45}}{2}}

    =\sqrt{\frac{1-\frac{\sqrt{2}}{2}}{2}}

    =\sqrt{\frac{2-\sqrt{2}}{4}}

    =\frac{\sqrt{2-\sqrt{2}}}{2}

    i.e, a = 2, b = 2, c = 2

    Do not spam posts all over the board, or you're likely to be banned.
    Last edited by DivideBy0; December 17th 2007 at 02:25 AM.
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  3. #3
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    Smile thanks

    and thanks for the spam tip, i don't really use these things so ya
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  4. #4
    Senior Member DivideBy0's Avatar
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    Well, feel free to post your problems if you have a lot, but don't post the same one in different forums.

    Anyhoo, welcome to Mathhelpforum
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