Re: How to instruct Math to take a certain (e.g. real) type of
- To: mathgroup at smc.vnet.net
- Subject: [mg105047] Re: How to instruct Math to take a certain (e.g. real) type of
- From: "Sjoerd C. de Vries" <sjoerd.c.devries at gmail.com>
- Date: Thu, 19 Nov 2009 05:22:34 -0500 (EST)
- References: <email@example.com>
You may try the RealOnly package available at
http://library.wolfram.com/infocenter/MathSource/6771/ . There may be
side effects, be careful.
Cheers -- Sjoerd
On Nov 18, 2:11 pm, Alexei Boulbitch <Alexei.Boulbi... at iee.lu> wrote:
> Dear Community,
> I came to a problem, that I cannot check the solution y=0 of equation
> In:= eq = (-8 + y)^(1/3) + (8 + y)^(1/3) == y^(1/3);
> eq /. y -> 0
> Out= False
> just because the expression
> In:= eq[] /. y -> 0
> Out= 2 + 2 (-1)^(1/3)
> Mathematica does not interpret as zero. And if I ask it to give a
> numerical answer
> In:= 2 + 2 (-1.)^(1/3)
> Out= 3.+ 1.73205 \[ImaginaryI]
> It returns the complex root out of the three possible.
> My question is the following:
> 1) How should I instruct Mathematica to take a certain root that I want
> of say, (-1)^(1/3)?
> 2) I think there is a general possibility instruct Mathematica that all
> calculations should be done on reals only. Is it right?
> Thank you, Alexei
> Alexei Boulbitch, Dr., habil.
> Senior Scientist
> IEE S.A.
> ZAE Weiergewan
> 11, rue Edmond Reuter
> L-5326 Contern
> Phone: +352 2454 2566
> Fax: +352 2454 3566
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