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Why is Mathematica giving me fits when I try to evaluate ArcCosh[Sqrt[2]]?

  1. Feb 19, 2009 #1
    For some reason, Mathematica will not comply when I try to determine

    [tex]
    \cosh^{-1}(\sqrt{2})
    [/tex]

    Why is this the case? Is [tex]\cosh^{-1}(x)[/tex] undefined there or something? If so, why? I don't really see it...

    Thanks!

    UPDATE: Looks like Maple 11 refuses to evaluate [tex]\cosh^{-1}(\sqrt{2})[/tex] too. What is going on here?!
     
    Last edited: Feb 19, 2009
  2. jcsd
  3. Feb 19, 2009 #2

    mgb_phys

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    Don't know, have you tried ln(x+root(x^2-1)) instead?
     
  4. Feb 19, 2009 #3

    Gokul43201

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    Last edited by a moderator: May 4, 2017
  5. Feb 19, 2009 #4

    CRGreathouse

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    http://www.research.att.com/~njas/sequences/A091648 [Broken]
     
    Last edited by a moderator: May 4, 2017
  6. Feb 19, 2009 #5
    It could be a problem if you have replaced this [itex]\sqrt{2}[/itex] with this [itex]2^{1/2}[/itex].
     
  7. Feb 19, 2009 #6

    Gokul43201

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    If the OP is looking for a decimal approximation, then something along the lines of Round[ArcCosh[Sqrt[2]],0.0001] should work just as well on Mathematica.
     
    Last edited by a moderator: May 4, 2017
  8. Feb 19, 2009 #7

    CRGreathouse

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    I thought the additional information there (inflection point, etc) might be relevant the the unstated underlying problem.
     
  9. Feb 19, 2009 #8

    uart

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    Hi AxiomOfChoice, what exactly do you mean by evaluate in this case? Maple will try to symbolically simply an expression, it wont return a decimal approximation unless you tell it to (typically using the "evalf" function.

    I've got Maple 7 and "evalf(arccosh(sqrt(2)));" returns 0.8813735866.
     
    Last edited: Feb 19, 2009
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