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Re: complex numbers

  • To: mathgroup at smc.vnet.net
  • Subject: [mg105908] Re: [mg105904] complex numbers
  • From: Murray Eisenberg <murray at math.umass.edu>
  • Date: Thu, 24 Dec 2009 20:58:59 -0500 (EST)
  • Organization: Mathematics & Statistics, Univ. of Mass./Amherst
  • References: <200912240516.AAA25894@smc.vnet.net>
  • Reply-to: murray at math.umass.edu

Such questions have been addressed many times before in this group.

You DON'T tell Mathematica in advance that x and y are to be real. 
Rather, when you want them to be interpreted as such, use ComplexExpand. 
  Thus:

   z
   ComplexExpand[Re[z]]
x
   ComplexExpand[Abs[z]]
Sqrt[x^2 + y^2]

Jon Joseph wrote:
> All: Something fundamental about complex number initialization I am 
> failing to understand. I wish to define a complex number
> 
> 	z=x+ I y where x and y are both reals. Can someone tell me the 
> proper way to tell Mathematica that x, y are real so that Re[z] returns 
> x and Im[z] returns y? Much appreciated, Jon.

-- 
Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305


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