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Thread: Unit circle - Convert cos to sin

  1. #1
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    Unit circle - Convert cos to sin

    What is $\displaystyle cos 480$ in terms of $\displaystyle sin$?
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  2. #2
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    Quote Originally Posted by nerdzor View Post
    What is $\displaystyle cos 480$ in terms of $\displaystyle sin$?
    $\displaystyle \cos (480 ^\circ) = -\frac{1}{2}$
    $\displaystyle \sin ^{-1} (-\frac{1}{2}) = -30^\circ = 210^\circ =330^\circ= 570^\circ$

    But for unit circle, we select $\displaystyle -30^\circ $ as we are measure as close to zero as possible. In other words, the range of $\displaystyle \sin ^{-1}$ is restricted to [–90, 90].
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