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Math Help - Addition Formulae

  1. #1
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    Addition Formulae

    Hey guys, im really stuck on a question from my maths homework, mainly because in school we have never done an addition formula with more than two terms in each set of brackets, any help would be greatly appreciated.

    This is what i have so far:

    (cosP+cosG+cosF)*+ (sinP+sinG+sinF)*
    = (cos*P+2cosPcosGcosF+cos*F) + (sin*P+2sinPsinGsinF+sin*F)
    = 1+1+(2cosPcosGcosF) + (2sinPsinGsinF)
    = 2+2(cosPcosGcosF+sinPsinGsinF)
    = 2+2cos(P-G-F)
    = 2[1+cos(P-G-F)]

    PS: the * refers to a squared term, i didnt know how to type it in the forum
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  2. #2
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    It is not at all clear form what you have posted what the objective is.
    But your algebra is lacking.
    \left( {\cos (x) + \cos (y) + \cos (z)} \right)^2  =  \cos ^2 (x) + \cos ^2 (y) + \cos ^2 (z) + 2\cos (x)\cos (y) + 2\cos (x)\cos (z) + 2\cos (y)\cos (z).
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  3. #3
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    Thanks for putting it so bluntly, yeah i know my algebra is poor, hence the reason im asking for help.

    Sorry about the clarity of my last post, i didnt really know how to put it into a clear question since the question in my homework only says "solve". Its on Addition Formulae though so i assumed someone here would know how to do it.

    I dont really understand what youve said there, i typed the eqautions into my calculator using random numbers and the expanded version comes out with a syntax error, is that just me inputting it wrong or something?? Sorry im really bad at maths.
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  4. #4
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    Quote Originally Posted by shaggy View Post
    i typed the eqautions into my calculator using random numbers and the expanded version comes out with a syntax error,
    You still have not told us what the question is asking!

    But thank you for being honest. You have actually made a point that I have said many times.
    “If someone does not know mathematics, calculators or computers are useless”.

    Now to your basic problem. I think that the help that you really need is not available in any forum such as this one. You need a one-on-one tutorial.
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