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Math Help - cosine problem

  1. #1
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    cosine problem

    " cos(x^2+5x+9)

    round answer to 4 decimal places. "
    Thanks!
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  2. #2
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    Re: cosine problem

    Quote Originally Posted by jonathanraxa View Post
    " cos(x^2+5x+9)

    round answer to 4 decimal places. "
    Thanks!
    what do you want done w/ this expression? directions?
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  3. #3
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    Re: cosine problem

    Quote Originally Posted by skeeter View Post
    what do you want done w/ this expression? directions?
    Sorry I forgot to mention. I'm trying to solve for 'x'
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    Re: cosine problem

    Quote Originally Posted by jonathanraxa View Post
    Sorry I forgot to mention. I'm trying to solve for 'x'
    then it would help to know ...

    \cos(x^2+5x+9) = \, ?
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  5. #5
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    Re: cosine problem

    Quote Originally Posted by skeeter View Post
    then it would help to know ...

    \cos(x^2+5x+9) = \, ?
    sorry again. It would equal 0
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  6. #6
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    Re: cosine problem

    Quote Originally Posted by jonathanraxa View Post
    sorry again. It would equal 0
    That means that x^2+5x+9 must be an odd multiple of \frac{\pi}{2}.
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  7. #7
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    Re: cosine problem

    if ...

    \cos(x^2+5x+9) = 0

    then ...

    x^2 + 5x + 9 = \frac{(2k+1)\pi}{2}

    k \in \mathbb{Z}
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  8. #8
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    Re: cosine problem

    Another thing I forgot to mention was that I'm trying to find the smallest positive number 'x' from this equation. I don't know if this helps in any way
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  9. #9
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    Re: cosine problem

    Quote Originally Posted by jonathanraxa View Post
    Another thing I forgot to mention was that I'm trying to find the smallest positive number 'x' from this equation. I don't know if this helps in any way
    Plato and I have laid the groundwork for a solution ... you figure out the specific solution using this last "forgotten" detail.

    Next time, try to post the entire problem as written.
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