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MathGroup Archive 2005

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Re: Bug in Reduce?

  • To: mathgroup at smc.vnet.net
  • Subject: [mg60425] Re: [mg60406] Bug in Reduce?
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Fri, 16 Sep 2005 03:49:05 -0400 (EDT)
  • Reply-to: hanlonr at cox.net
  • Sender: owner-wri-mathgroup at wolfram.com

$Version

5.2 for Mac OS X (June 20, 2005)

Reduce[{a c-b d==0,a d+b c==0},
    {a,b,c,d},Reals]//Simplify

(a == 0 && b == 0) || (c == 0 && d == 0)


Bob Hanlon

> 
> From: "Kennedy" <jack at realmode.com>
To: mathgroup at smc.vnet.net
> Date: 2005/09/15 Thu AM 05:16:26 EDT
> Subject: [mg60425] [mg60406] Bug in Reduce?
> 
> The source of this apparent bug could be my misunderstanding of the 
middle, 
> "vars" parameter of Reduce, but it sure seems like the following output 
> indicates that  c  must be  0  for my two equations to be satisfied, when in 
> fact if  a  and  b  are both  0,  c  does not need to be  0.
> 
> Regards,
> Jack
> 
> In[1]:=
> Reduce[{a c - b d == 0, a d + b c == 0}, {a, b, c, d}, Reals] // 
> FullSimplify
> 
> Out[1]=
> c == 0 && (d == 0 || (a == 0 && b == 0))
> 
> (version 5.1 for Windows) 
> 
> 


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