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Math Help - Trigonometric equations

  1. #1
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    Trigonometric equations

    Find the general solutions of:
    cos 50 + cos 30 = 0
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  2. #2
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    Quote Originally Posted by LilDragonfly
    Find the general solutions of:
    cos 50 + cos 30 = 0
    I presume you know that given,
    \cos x=a you know what to find all the solutions.
    ---------
    Use cosine angle sum identity on,
    \cos 5x+\cos 3x=0
    To get,
    2\cos 4x\cos x=0
    Thus, each factor is zero,
    \cos 4x=0
    \cos x=0
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