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Math Help - cos2pi

  1. #1
    Senior Member furor celtica's Avatar
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    Thumbs down cos2pi

    why is cos2pi = +- 1? its not logical, since cosA = sinA/tanA and sin A = tan A = 0....
    ??
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  2. #2
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    Quote Originally Posted by furor celtica View Post
    why is cos2pi = +- 1? its not logical, since cosA = sinA/tanA and sin A = tan A = 0....
    ??
    2\pi radians is a full revolution of the unit circle. So you end up back exactly where you started at an angle of 0, and so the horizontal distance (the cosine) will be exactly the same.

    What's \cos{0} equal?


    BTW you can't work out \cos{2\pi} = \frac{\sin{2\pi}}{\tan{2\pi}} because the function \tan{x} is defined by \frac{\sin{x}}{\cos{x}}.

    It would be the same as saying you're trying to find x if x = x...
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