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Thread: finding and angle x in radians?

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    finding and angle x in radians?

    Find an angle x in radians such that 8pi<x<9pi and cosx=1/2

    What is this question asking for? I came up with pi/3, but I don't think that's in between 8 and 9 pi. Can anyone explain? Thanks
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    Quote Originally Posted by captaintoast87 View Post
    Find an angle x in radians such that 8pi<x<9pi and cosx=1/2

    What is this question asking for? I came up with pi/3, but I don't think that's in between 8 and 9 pi. Can anyone explain? Thanks
    Remember that $\displaystyle \cos{x}$ is periodic with a a period of $\displaystyle 2\pi$ which means you get your original answer of $\displaystyle \frac{\pi}{3}$ and add 4 lots of $\displaystyle 2\pi$ (this is 4 periods) to give you an answer of $\displaystyle 8\pi + \frac{\pi}{3} = \frac{25\pi}{3}$
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