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MathGroup Archive 2004

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Re: Incomplete simplification

  • To: mathgroup at smc.vnet.net
  • Subject: [mg49293] Re: Incomplete simplification
  • From: BobHanlon at aol.com
  • Date: Mon, 12 Jul 2004 02:11:34 -0400 (EDT)
  • Sender: owner-wri-mathgroup at wolfram.com

Simplify works with this on my version


$Version

5.0 for Mac OS X (November 19, 2003)


S={{0,-x31,x21},{x31,0,-x11},{-x21,x11,0},{0,-x32,x22},{x32,0,-x12},{-x22,x12,
0}};

G=PseudoInverse[S];


G1=Simplify[G,   Element[Cases[S, _Symbol,Infinity], Reals]];


G2=ComplexExpand[G];


G1==G2 // Simplify


True


Bob Hanlon

> In a message dated Sun, 11 Jul 2004 06:26:30 +0000 (UTC), 
> carlos at colorado.edu writes:<BR><BR>Using Mathematica 4.2 on a mac I defined a 6 x 3 
> symbolic
> matrix and take its Moore-Penrose inverse:
> 
> S={{0,-x31,x21},{x31,0,-x11},{-x21,x11,0},{0,-x32,x22},
>        {x32,0,-x12},{-x22,x12,0}};
> G=PseudoInverse[S];   
> 
> Mathematica thinks the entries are complex, so it returns a
> result with Conjugate[x11], etc.   To get rid of them I tried
> 
> G=Simplify[G,x11\[Element]Reals&&x21\[Element]Reals    <...> ];
> 
> But the Conjugate[...] are still there. Fortunately G=ComplexExpand[G]
> works. But why is Simplify unable to use the reality assumptions?
> 


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