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MathGroup Archive 2000

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Re: number types

  • To: mathgroup at
  • Subject: [mg21650] Re: number types
  • From: Harald Giese <giese at>
  • Date: Fri, 21 Jan 2000 03:59:59 -0500 (EST)
  • Organization: Institut fuer Meereskunde, Universitaet Hamburg
  • References: <861529$>
  • Sender: owner-wri-mathgroup at

Naum Phleger wrote:
>     I feel sort of silly asking something that should be so clear but after
> LOTS of trying I can't seem to get it right.
> How can I make Mathematica know that a variable is real or positive so that
> Conjugate[a] gives a
> Sqrt[ a^2 ] gives a
> when I evaluate integrals with a in them it doesn't give me an If statement
> like


You have to tell Mathematica the property within the expression:

In[1]:= Simplify[Conjugate[a], a \[Element] Reals]
Out[1]= a

In[2]:= Simplify[Sqrt[a^2], a \[Element] Reals]
Out[2]= Abs[a]

> If[ Im[a]=0, answer I want   , unevaluated integral ]
Please note: "Equal[]" is abbreviated as "==", not "=".


--- This message was entirely written using recycled electrons ---

Harald Giese
Email: giese at
Phone: +49 (0)40 42838 5796; Fax: +49 (0)40 5605724
Institut fuer Meereskunde der Universitaet Hamburg
(Institute of Oceanography of the University of Hamburg)
Troplowitzstrasse 7, D-22529 Hamburg

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