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Thread: Inverse function problem

  1. #1
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    Inverse function problem

    Hello
    I have a folllowing question
    Function A(r)=2*pi*r2+6*pi*r. I has a an inverse function r(A)=(-6*pi+-sqrt(4*pi(9*pi+2r))/4*pi
    Calculate at what radius does the area of the cylinder equal 200. do i just make the function r(A)=200? ThanksInverse function problem-1.pngInverse function problem-2.png
    Last edited by dbag; May 27th 2019 at 05:15 AM.
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  2. #2
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    Re: Inverse function problem

    it should be

    $\displaystyle r=\frac{-6 \pi + \sqrt{4\pi (9 \pi +2A)}}{4 \pi }
    $

    now replace $A=200$
    Last edited by Idea; May 27th 2019 at 07:15 AM.
    Thanks from topsquark and dbag
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  3. #3
    MHF Contributor
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    Re: Inverse function problem

    Quote Originally Posted by dbag View Post
    I has a an inverse function r(A)=(-6*pi+-sqrt(4*pi(9*pi+2r))/4*pi
    This is a very bad mistake. Understanding what a function is and isn't is SO fundamental. Please review the definition.
    Thanks from topsquark
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