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Math Help - half angle conversion formulas

  1. #1
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    half angle conversion formulas

    sinA+sinB+sinC=4cos1/2Acos1/2Bcos1/2C

    ..guys can you help me in proving this one..tnx..
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  2. #2
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    Re: half angle conversion formulas

    Yikes this is hard to read, some brackets or spaces would be nice ><

    Is it \displaystyle \begin{align*} \sin{(A)} + \sin{(B)} + \sin{(C)} = 4\cos{\left( \frac{A}{2} \right)} \cos{\left( \frac{B}{2}\right)}\cos{\left( \frac{C}{2}\right)} \end{align*}?
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    Re: half angle conversion formulas

    Quote Originally Posted by fireboy25 View Post
    sinA+sinB+sinC=4cos1/2Acos1/2Bcos1/2C

    ..guys can you help me in proving this one..tnx..
    What have you been able to do with this so far?

    -Dan
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    Re: half angle conversion formulas

    Also must write the condition for this question we should have A + B + C = 180 degree.
    Then use the sum and product formula: sin P + sin Q = 2 sin ( P+Q)/2 cos ( P-Q)/2 etc.
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    Re: half angle conversion formulas

    Quote Originally Posted by ibdutt View Post
    Also must write the condition for this question we should have A + B + C = 180 degree.
    That's only if A, B, C are angles in a triangle. But it's a good question.

    @fireboy25: Are A, B, and C the angles of a triangle?

    -Dan
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    Re: half angle conversion formulas

    half angle conversion formulas-28-sep-13.png
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    Re: half angle conversion formulas

    yes..the sum of A, B, C is 180..
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