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Re: Matrix inverse not evaluating

• To: mathgroup at smc.vnet.net
• Subject: [mg41643] Re: [mg41593] Matrix inverse not evaluating
• From: Murray Eisenberg <murraye at attbi.com>
• Date: Thu, 29 May 2003 08:14:13 -0400 (EDT)
• Organization: Mathematics & Statistics, Univ. of Mass./Amherst
• References: <200305280857.EAA09493@smc.vnet.net>
• Reply-to: murray at math.umass.edu
• Sender: owner-wri-mathgroup at wolfram.com

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

• Follow-Ups:
  • Re: Re: Matrix inverse not evaluating
    • From: Murray Eisenberg <murraye@attbi.com>

• References:
  • Matrix inverse not evaluating
    • From: gregory.lypny@videotron.ca (Gregory Lypny)