Re: Bug in Reduce?

*To*: mathgroup at smc.vnet.net*Subject*: [mg60470] Re: Bug in Reduce?*From*: Jean-Marc Gulliet <jeanmarc.gulliet at gmail.com>*Date*: Sat, 17 Sep 2005 02:31:51 -0400 (EDT)*Organization*: The Open University, Milton Keynes, U.K.*References*: <dgdulf$1ad$1@smc.vnet.net>*Sender*: owner-wri-mathgroup at wolfram.com

Bob Hanlon wrote: > $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: [mg60470] 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) >> >> > > In[1]:= FullSimplify[Reduce[{a*c - b*d == 0, a*d + b*c == 0}, {a, b, c, d}, Reals]] Out[1]= (a == 0 && b == 0) || (c == 0 && d == 0) In[2]:= $Version Out[2]= "5.2 for Microsoft Windows (June 20, 2005)" Regards, /J.M.