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Math Help - Intersection of a circular function and a cubic

  1. #1
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    Intersection of a circular function and a cubic

    Not really sure how to approach this one analytically, any clues?

    x3 +2x = 5cos x

    Cheers,
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  2. #2
    MHF Contributor MarkFL's Avatar
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    Re: Intersection of a circular function and a cubic

    You cannot solve for x explicitly, you will need to use a numeric root finding technique, such as Newton's method to approximate the root. This is a method from differential calculus.
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  3. #3
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    Re: Intersection of a circular function and a cubic

    Oh I see, well I'm not familiar with such a technique so I guess a graphical solution will have to suffice. Thank you Mark!
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  4. #4
    MHF Contributor MarkFL's Avatar
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    Re: Intersection of a circular function and a cubic

    You should find x\approx0.96707029542400250809. This is what the computer returns, using a numeric method.
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