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Math Help - Solving an equation in a specified interval

  1. #1
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    Solving an equation in a specified interval

    The Question: Solve the equation in the interval 0 < θ < 2 pi.

    cos θ + cos2 θ + sin2 = 0

    Attempted Solution: Well, my hunch was to factor this equation. But, at least to my innumerate eye, it looks as if it cannot be factored. I am a bit confused by the structure of this equation. I'm not use to seeing anything like "sin" without a θ. The answers probably really easy and maybe it's just tiredness preventing me from seeing the solution, but could someone help?
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  2. #2
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    is the middle term \cos(2\theta) or \cos^2{\theta} ?

    btw, \sin(2) is just a constant.
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  3. #3
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    Quote Originally Posted by skeeter View Post
    is the middle term \cos(2\theta) or \cos^2{\theta} ?

    btw, \sin(2) is just a constant.
    It's \cos^2{\theta}.

    Sorry about the error.

    Equation rewritten:

    \cos{\theta} + \cos^2{\theta} + \sin^2.
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  4. #4
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    \cos^2{\theta} + \cos{\theta} + \sin(2) = 0

    looks quadratic to me ...

    only problem is b^2 - 4ac < 0

    what's that tell you?
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