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: <he0oa3$4or$1@smc.vnet.net>
Hi Alexei, 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[345]:= eq = (-8 + y)^(1/3) + (8 + y)^(1/3) == y^(1/3); > eq /. y -> 0 > > Out[346]= False > > just because the expression > > In[347]:= eq[[1]] /. y -> 0 > > Out[347]= 2 + 2 (-1)^(1/3) > > Mathematica does not interpret as zero. And if I ask it to give a > numerical answer > In[348]:= 2 + 2 (-1.)^(1/3) > > Out[348]= 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 > Luxembourg > > Phone: +352 2454 2566 > Fax: +352 2454 3566 > > Website:www.iee.lu > > This e-mail may contain trade secrets or privileged, undisclosed or other wise confidential information. If you are not the intended recipient and have received this e-mail in error, you are hereby notified that any review, copying or distribution of it is strictly prohibited. Please inform us immediately and destroy the original transmittal from your system. Thank you for your co-operation.