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MathGroup Archive 2005

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Re: Complex numbers in Mathematica

  • To: mathgroup at
  • Subject: [mg61699] Re: [mg61647] Complex numbers in Mathematica
  • From: "Jose Luis Gomez" <jose.luis.gomez at>
  • Date: Wed, 26 Oct 2005 01:01:58 -0400 (EDT)
  • Sender: owner-wri-mathgroup at


I do get the correct complex number answer in my Mathematica 5.2

My guess is that somehow you loaded the RealOnly package in your Mathematica
session (Or maybe your Teacher's edition automatically loads this package? I
do Not know).

Here is the help about RealOnly:

The package RealOnly was created in order to adapt Mathematica to students
that do not know about complex numbers. For example, students "know" that
the cubic root of -8 is -2. This is Not correct, the *main* cubic root of -8
is a complex number. Mathematica will give you the correct complex answer,
however if you load the package RealOnly, then Mathematica will change its
behavior and it will answer that the cubic root of -8 is -2. 

I hope that helps
Jose Luis

-----Mensaje original-----
De: "Per Rønne" [mailto:per at RQNNE.invalid] 
Enviado el: Lunes, 24 de Octubre de 2005 08:07 p.m.
Para: mathgroup at
Asunto: [mg61647] Complex numbers in Mathematica

If I write:

In[8]=Factor[(5 - 3I) + (-4 + I)x + (1 - I)x^2]

I get
Nonreal::"warning": "Nonreal number encountered."
Out[8]= Nonreal

The same with Sqrt[-1].

Why doesn't it show the complex numbers? According to the books it
should - is it a matter of preferences set?

I'm using Mathematica Teacher's Edition 1.1 on MacOS X.
Per Erik Rønne

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