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MathGroup Archive 2005

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Bug in Reduce?

  • To: mathgroup at
  • Subject: [mg60406] Bug in Reduce?
  • From: "Kennedy" <jack at>
  • Date: Thu, 15 Sep 2005 05:16:26 -0400 (EDT)
  • References: <dfrhi4$g4l$> <dg8lfv$r8g$> <>
  • Sender: owner-wri-mathgroup at

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.


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

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

(version 5.1 for Windows) 

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