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  1. #1
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    trig help

    Find the coordinates of 57pi/3.

    but they're not giving me the period, how am i supposed to know?
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    Quote Originally Posted by NeedHelp18 View Post
    Find the coordinates of 57pi/3.
    Huh? Do you mean the coordinates of the point on the unit circle that corresponds to that angle? Give the problem exactly as it is stated.
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    Yes, on the unit circle.
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    Quote Originally Posted by NeedHelp18 View Post
    Yes, on the unit circle.
    The coordinates of any point on the unit circle corresponding to the angle \theta are (\cos\theta,\,\sin\theta).

    So how do you find the sine and cosine of \frac{57\pi}3? Well, first you should reduce that fraction. Now what is the sine and cosine of any odd multiple of \pi?
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    could i do (54pi/3 + pi)

    if so, then what?
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    Quote Originally Posted by NeedHelp18 View Post
    could i do (54pi/3 + pi)
    What? Is it \frac{57\pi}3 or \frac{54\pi}3? In either case, do as I said and simplify the fraction first. What is 54 (or 57) divided by 3?
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    so it would be 19pi? after i divide it by 3

    are the coordinates (1, 0)?
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    Quote Originally Posted by NeedHelp18 View Post
    so it would be 19pi? after i divide it by 3

    are the coordinates (1, 0)?
    Try again with the x-coordinate. What is the cosine of an odd multiple of \pi?
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    is it -1?
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    Quote Originally Posted by NeedHelp18 View Post
    is it -1?
    Yes. The angle 19\pi is coterminal with \pi, and \cos\pi=-1.
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