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Suggest a function

  1. Sep 28, 2008 #1
    Can anyone give me a function that (roughly) looks like the top or bottom one in the picture attached? And yes the limits is constant as x-> +/- infinity. I don't want a trig function like arctan since trig isn't really all that applicable for what I'm doing.

    I'm posting here since I definitely saw functions like this in my deff eq class, but have unfortunately forgotten its formula.

    Thanks.
     

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  3. Sep 28, 2008 #2

    arildno

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    Well, the hyperbolic tangent function can achieve such behaviour easily, with addition of a constant, sign choice and scaling.
    Similarly with the arctan function
     
  4. Sep 28, 2008 #3
    you missed the part where I said that I didn't want trig functions.
     
  5. Sep 28, 2008 #4

    Hootenanny

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    tanh isn't a trigonometric function.
     
  6. Sep 28, 2008 #5
    what about

    [tex]f(x)=- x^{\frac{1}{3}},if,x\geq 0;(-x)^{\frac{1}{3}}, if, x<0[/tex] this is a piecewise defined funct.
     
    Last edited: Sep 28, 2008
  7. Sep 28, 2008 #6

    statdad

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    Look at the class of logistic functions.
     
  8. Sep 28, 2008 #7
    Mine doesn't really work, since i didn't see the restriction that it has to have a horizontal asymptote.
     
  9. Sep 29, 2008 #8

    Integral

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  10. Sep 29, 2008 #9

    arildno

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    What nonsense.
    Do you think you can't "apply" an arctan function just because you are not dealing with a problem in trigonometry???
     
  11. Sep 29, 2008 #10
    Have you got accurate numerical values or just the shape of the graph? If you got numerical data you could take a shot at exactly guessing the function.
     
  12. Sep 29, 2008 #11
    just use integral's curves lawl
     
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