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Math Help - Cos addition identity but with a multiplyier

  1. #1
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    Cos addition identity but with a multiplyier

    i hope that someone can help, i have a equation that is in the form

    cos(s)cos(t)–Asin(s)sin(t)

    i want to simplify it using the simple trig identity

    cos(s+t)=cos(s)cos(t)–sin(s)sin(t)

    but i don't think that i can because of the A multiplying term, anyone know of another way that you can or if you defiantly can't
    Cheers
    WN
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  2. #2
    MHF Contributor
    Joined
    Mar 2007
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    1,240

    Talking

    Without knowing the exact expression in question, it's hard to say for sure. But you could, I suppose, so something like the following:

    . . . . .cos(s)cos(t) – Asin(s)sin(t) = [cos(s)cos(t) - sin(s)sin(t)] - (A - 1)sin(s)sin(t)

    I don't know if that will help at all, though....
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  3. #3
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    well attached is the whole equation
    Cheers
    WN
    Attached Thumbnails Attached Thumbnails Cos addition identity but with a multiplyier-formula-simplify.jpg  
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