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Math Help - cos question

  1. #1
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    cos question

    Please help me solve this problem.... it's been awhile so I am a bit rusty!
    Thanks

    cos x + 2 cos x = -1 over the interval [0, 2 p)
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  2. #2
    A riddle wrapped in an enigma
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    Quote Originally Posted by kittykat7 View Post
    Please help me solve this problem.... it's been awhile so I am a bit rusty!
    Thanks

    cos x + 2 cos x = -1 over the interval [0, 2 p)
    Hi kittykat7,

    I'm going to assume that you meant to write:

    \cos^2x+2 \cos x=-1

    In which case,

    \cos^2 x+2\cos x+1=0

    (\cos x+1)^2=0

    \cos x=-1

    x=\{\pi\}
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  3. #3
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    Quote Originally Posted by masters View Post
    Hi kittykat7,

    I'm going to assume that you meant to write:

    \cos^2x+2 \cos x=-1

    In which case,

    \cos^2 x+2\cos x+1=0

    (\cos x+1)^2=0

    \cos x=-1

    x=\{\pi\}

    Thanks, I'm actually not sure what it was asking, that is how I received the question. That is one of the choices for an answer, so I am assuming that is what I was asking. Thank you for your speedy response!
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