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MathGroup Archive 2005

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Re: Why does Inverse[M] hesitate?

  • To: mathgroup at
  • Subject: [mg54460] Re: Why does Inverse[M] hesitate?
  • From: Peter Pein <petsie at>
  • Date: Sun, 20 Feb 2005 00:11:35 -0500 (EST)
  • References: <cv6t0c$6re$>
  • Sender: owner-wri-mathgroup at

Skirmantas wrote:
> The Inverse function sometimes calculates the inverse of a matrix
> immediately, sometimes it does not. Try this example in Mathematica
> 5.1:
> A={{(1-g)-1,1},{-w P(1-g)/C,-1}}//MatrixForm
> B={{0},{-P(w+1)}}//MatrixForm
> I get 
> Out: Inverse[(expanded A)].(expanded B)
> If I do just 
> A={{a,b},{c,d}}
> B={{e},{f}}
> Inverse[A].B 
> I get the final correct result. 
Inverse and Dot are not defined for MatrixForm[{{...}}].

   ( A={{(1-g)-1,1},{-w P(1-g)/C,-1}} )//MatrixForm
   ( B={{0},{-P(w+1)}} )//MatrixForm

and it will work as expected.

Peter Pein

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