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Re: Re: Matrix inverse not evaluating

• To: mathgroup at smc.vnet.net
• Subject: [mg41686] Re: [mg41643] Re: [mg41593] Matrix inverse not evaluating
• From: Murray Eisenberg <murraye at attbi.com>
• Date: Fri, 30 May 2003 03:56:30 -0400 (EDT)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200305280857.EAA09493@smc.vnet.net> <200305291214.IAA03947@smc.vnet.net>
• Reply-to: murray at math.umass.edu
• Sender: owner-wri-mathgroup at wolfram.com

Correction: the line following "Instead ... following:" should be:

     math = { { 1, 2}, {3, 4} };

Murray Eisenberg wrote:
> Did you do something like the following (which I show for a 2-by-2 
> instead of 3-by-3)?
> 
>    mat = MatrixForm[{ { 1, 2}, {3, 4} }]
>    Inverse[mat]
> 
> If so, then that's why you obtained the result you did:  MatrixForm 
> merely specifies a printing form of its argument.  That printing form is 
> NOT itself a matrix -- a matrix being, to Mathematica, a certain list of 
> lists -- and so you cannot expect to be able to take an inverse of it or 
> do any other matrix operation upon it.
> 
> Instead, you need to do something like the following:
> 
>     mat = MatrixForm[{ { 1, 2}, {3, 4} }]
>     Inverse[mat]
> 
> Or, if you want to see the original matrix and its inverse displayed in 
> the traditional way:
> 
>     mat = {{1, 2}, {3, 4}}; MatrixForm[mat]
>     inv = Inverse[mat]; MatrixForm[inv]
> 
> 
> Gregory Lypny wrote:
> 
>>Yet another newbie question: I have a 3x3 matrix called V, filled with
>>numbers, whose output displays correctly.  However, when I enter
>>Inverse[V] the output displayed is not the answer but the word Inverse
>>followed by the the argument matrix as Inverse[(elements of V)].  What
>>am I doing wrong?  Gregory
>>
>>
> 
> 

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Murray Eisenberg                     murray at math.umass.edu
Mathematics & Statistics Dept.
Lederle Graduate Research Tower      phone 413 549-1020 (H)
University of Massachusetts                413 545-2859 (W)
710 North Pleasant Street            fax   413 545-1801
Amherst, MA 01003-9305

• References:
  • Matrix inverse not evaluating
    • From: gregory.lypny@videotron.ca (Gregory Lypny)
  • Re: Matrix inverse not evaluating
    • From: Murray Eisenberg <murraye@attbi.com>