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Math Help - Solving a trigonometric equation

  1. #1
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    Solving a trigonometric equation

    Solve on the domain 0 ≦ x ≦ 360. Use a calculator and round to the nearest degree if unable to use special triangles.

    cos x-1 = -cos x

    Can anyone give me some pointers on this one? I'm taking grade 12 math through an independent learning course, where I have no access to a teacher, and this question has me completely stuck.

    I've solved other trig equations by isolating x and using a special triangle, a calculator, or simply looking at the graph sometimes. However, the right side of the equation has always been a real number in the past, and I'm not sure what to do with this -cos x.
    Last edited by Lethargic; December 3rd 2012 at 07:34 AM.
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  2. #2
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    Re: Solving a trigonometric equation

    Is it cos (x) - 1 or cos(x-1)?
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  3. #3
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    Re: Solving a trigonometric equation

    It is cos x - 1

    No brackets written whatsoever
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  4. #4
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    Re: Solving a trigonometric equation

    If it is cos x - 1 = -cos x
    then 2cos x = 1
    cos x = 1/2
    x = phi/3 and 5 phi/3
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  5. #5
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    Re: Solving a trigonometric equation

    Thanks! I was over-thinking that far too much
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  6. #6
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    Re: Solving a trigonometric equation

    Quote Originally Posted by Lethargic View Post
    It is cos x - 1
    No brackets written whatsoever

    Please learn to use correct notation. The cosine is a function and as such it should be written in function notation: \cos(x).
    You would not write f\,x for f(x), would you?
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  7. #7
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    Re: Solving a trigonometric equation

    Tell that to whomever wrote my textbook
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  8. #8
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    Re: Solving a trigonometric equation

    Quote Originally Posted by coolge View Post
    If it is cos x - 1 = -cos x
    then 2cos x = 1
    cos x = 1/2
    x = pi/3 and 5 pi/3
    ...
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