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Re: Why is this so?

  • To: mathgroup at
  • Subject: [mg15342] Re: Why is this so?
  • From: "Atsushi ODA" <a-oda at>
  • Date: Fri, 8 Jan 1999 04:15:29 -0500
  • Organization: BIGLOBE dial-up user
  • References: <76pq9g$>
  • Sender: owner-wri-mathgroup at

Chester Lin wrote in message <76pq9g$e0n at>...
>Isn't it true that (-125)^(1/3) == -5?
>Why do I get this strange result?
>I am using Mathematica 3.01 for Students on Macintosh.
>Thanks for any info.
>Chester Lin
>chester at

Usually, Mathematica treated every number as complex. So in your case,
you have three values for  (-125)^(1/3) such as -5*(1/2+Sqrt[3]/2
I),-5*(1/2-Sqrt[3]/2 I) and -5.  That's why mathematica tell "not a
machine-size *real* number".

Solution is easy. Just load standard package, "Miscellaneous`RealOnly`
". You should consult standard package manual,  then you will find
exactly same example of yours.

Atsushi ODA <a-oda at> Kawasaki, JAPAN

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