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Math Help - Trigonometric Function

  1. #1
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    Trigonometric Function

    The inverse of Cos x is a function. The domain of Cos x could be ???


    How would I find the domain???
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  2. #2
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    In order for \textrm{Cos}\,{x} to have an inverse function, it must be one-to-one.

    Draw the function \cos{x}. Can you choose a domain where there aren't any repeating y values?
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  3. #3
    Senior Member eumyang's Avatar
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    Hmm... I'm assuming that the fact that C is capitalized is significant. I only learned f(x) = \cos \,x when I was in school, and had never seen f(x) = Cos \,x until now. Is it a regional/national thing? I'm in the US.
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  4. #4
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    The capitalisation means there has been a standard restriction on the domain of \cos{x}. It's up to you to find what that domain is.

    Like I said, draw the function, and choose a domain in which there are not any repeating y values.
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  5. #5
    Senior Member MacstersUndead's Avatar
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    Try looking at this interval.

    [0,\pi]

    edit:// mind blanked.
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  6. #6
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    Quote Originally Posted by MacstersUndead View Post
    Try looking at this interval.

    [0,\pi]

    edit:// mind blanked.
    Well thanks for telling the OP the answer :|

    Now, can you see WHY they would restrict the domain to be [0, \pi]?
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