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Math Help - Tricky operation

  1. #1
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    Poland
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    Tricky operation

    Hello

    I need some help. And I haven't recived any help at the forums in my country. We have to calculate:
    cos10degrees * cos20degrees * cos40degrees .
    It's very important..
    One more time, sorry for my english
    Last edited by Fele93; March 26th 2012 at 10:21 AM.
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  2. #2
    Senior Member
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    Re: Tricky operation

    There is a formula which says cos(2alpha)=2cos^2(alpha)-1
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  3. #3
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    Re: Tricky operation

    Ok but.. How can I use it there?
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  4. #4
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    Re: Tricky operation

    Get cos40 in terms of cos20 and then cos80 in terms of cos40 and then use your first answer again.
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