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MathGroup Archive 1999

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Re: New user question

  • To: mathgroup at
  • Subject: [mg20400] Re: New user question
  • From: "Allan Hayes" <hay at>
  • Date: Tue, 26 Oct 1999 00:32:53 -0400
  • References: <7uefh0$>
  • Sender: owner-wri-mathgroup at

Thomas Moriarty <moriarty at> wrote in message
news:7uefh0$277 at
> I have just begun to use/learn Mathematica.  One of the first things I
> tried was to Plot[x^(1/3),{x,-5,5}] and got error messages indicating that
> the negatives^(1/3) were not machine level real numbers (or close to
> that) - the positive side displayed ok.
> What am I doing wrong?
> Thanks

You are not doing anything wrong - its that in the complex numbers, which is
what Mathematica uses, we have

(-1)^(1/3) // ComplexExpand

        1/2 + (I*Sqrt[3])/2

You might like to look at the standard add on package

Allan Hayes
Mathematica Training and Consulting
Leicester UK
hay at
Voice: +44 (0)116 271 4198
Fax: +44 (0)870 164 0565

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