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Homework Help: Some problems with me

  1. Nov 19, 2006 #1
    Hi all,,

    i hope you could help me in the two problem below:uhh:

    1-2piCOS(2piX)=0

    and

    y=exp(x-1)-x
    i want here x in terms of y

    thanx for help:rolleyes:
     
  2. jcsd
  3. Nov 19, 2006 #2

    HallsofIvy

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    Science Advisor

    ??? It's not clear to me what you are asking. There is no "y" in the first equation so x cannot be written "as a function of y", it is a constant: [itex]cos(2\pix)= 1/(2\pi)[/itex] so x= 1/(2\pi)cos^{-1}(1/(2\
    pi)[/itex].

    If the second equation is independent of the first, the x can be written as a y, but not using "elementary" functions. You should be able to write it in terms of "Lambert's W function" which is defined as the inverse function to f(x)= xex.
     
  4. Nov 21, 2006 #3
    hi man and thank you for reply,,

    its big problem for me and im really want help:
    the first equation is
    f(x)=x-sin(2pix) and they want from me to find the absolute maximum and absolute minimum of f(x)????



    the second equation is independent of the first
    y=exp(x-1)-x

    the question is
    f(x)=exp(x-1)-x
    find the inverse
    so i want x=0.5y+1(for example)
    i sure that you know the inverse, so i wait your answer

    thank you for reply my dear:smile:
     
  5. Nov 21, 2006 #4
    There is no absolute max or min. [tex]\displaystyle\lim_{x\to\infty} x-\sin(2\pi x)=\infty[/tex] and [tex]\displaystyle\lim_{x\to-\infty} x-\sin(2\pi x)=-\infty[/tex].
     
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