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Math Help - complex numbers, a question

  1. #1
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    complex numbers, a question

    Why is

    r(cos(-x) + isin(-x) = r(cos(x) - isin(x))?

    Where does the negative in the cos go?
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  2. #2
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    The cosine function is an even function: cos(-x)=cos(x).
    The sine function is an odd function: sin(-x)=-sin(x).
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