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MathGroup Archive 2006

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Re: Strange empty set of solutions

  • To: mathgroup at smc.vnet.net
  • Subject: [mg71793] Re: Strange empty set of solutions
  • From: Jens-Peer Kuska <kuska at informatik.uni-leipzig.de>
  • Date: Wed, 29 Nov 2006 02:56:35 -0500 (EST)
  • Organization: Uni Leipzig
  • References: <ekh7pg$sgs$1@smc.vnet.net>
  • Reply-to: kuska at informatik.uni-leipzig.de

Hi,

and we can't read you mind and the memory of your computer
so we must imagine a matrix M and write down

Solve[{{{1, 2, 3}, {2, 4, 6}, {1, -10, 0}}.{a, b, c} == {0, 0, 0},
   a^2 + b^2 + c^2 == 1}, {a, b, c}]

and got two solutions ...

Regards
   Jens

José Carlos Santos wrote:
> Hi all,
> 
> I have a certain 3 x 3 numerical matrix M. If I type
> 
> Solve[M.{a,b,c}=={0,0,0},{a,b,c}]
> 
> I get
> 
> {{a -> 0. + 0.0410026 c, b -> 0. + 1.35294 c}}
> 
> However, if I type
> 
> Solve[{M.{a,b,c}=={0,0,0},a^2+b^2+c^2==1},{a,b,c}]
> 
> I get the empty set. Why is that? I should get two solutions!
> 
> Best regards,
> 
> Jose Carlos Santos
> 


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