       Re: Why is this so?

• To: mathgroup at smc.vnet.net
• Subject: [mg15328] Re: [mg15304] Why is this so?
• From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
• Date: Fri, 8 Jan 1999 04:15:18 -0500
• Organization: Universitaet Leipzig, Institut fuer Informatik
• References: <199901040721.CAA14333@smc.vnet.net.>
• Sender: owner-wri-mathgroup at wolfram.com

```Hi Chester,

no it is not true that (-125)^(1/3) == -5

it is true that (-5)^3 == -125 but there are two other numbers (5
*(-1)^1/3) and (-5*(-1)^(2/3).

Mathematica need to know witch one you mean.

Regards
Jens

Chester Lin wrote:

> The following in/out does not make sense to me:
>
> Clear[f, x]
> f[x_] := x^(1/3)
> Plot[f[x], {x, -125, 125}]
>
> Plot::plnr : f[x] is not a machine-size real number at x = -125..
> Plot::plnr : f[x] is not a machine-size real number at x = -114.858.
> Plot::plnr : f[x] is not a machine-size real number at x = -103.798.
> General::stop :
>  Further output of Plot::plnr will be suppressed during this
> calculation.
>
> 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 nicco.sscnet.ucla.edu

```

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