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Re: Mathematica bug??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100575] Re: [mg100540] Mathematica bug??
  • From: Bob Hanlon <hanlonr at cox.net>
  • Date: Mon, 8 Jun 2009 02:08:20 -0400 (EDT)
  • Reply-to: hanlonr at cox.net

$Version

7.0 for Mac OS X x86 (64-bit) (February 19, 2009)

mat = {{Sqrt[1 - 2/r], 0, 0, 0}, {0, 1/Sqrt[1 - 2/r], 0, 0}, {0, 0, r,
     0}, {0, 0, 0, r Sin[\[Theta]]}};

inv = mat // Inverse

{{1/Sqrt[1 - 2/r], 0, 0, 0}, 
   {0, Sqrt[1 - 2/r], 0, 0}, 
   {0, 0, 1/r, 0}, {0, 0, 0, 
     Csc[\[Theta]]/r}}

mat == (inv // Inverse)

True


Bob Hanlon

---- oshaughn <oshaughn at gravity.psu.edu> wrote: 

=============
{{Sqrt[1 - 2/r], 0, 0, 0}, {0, 1/Sqrt[1 - 2/r], 0, 0}, {0, 0, r,
   0}, {0, 0, 0, r Sin[\[Theta]]}} // Inverse

gives

{{0, 0, 0, 0}, {0, 0, 0, 0}, {0, 0, 1/r, 0}, {0, 0, 0, Csc[\[Theta]]/
  r}}

with no warnings.  This is a *diagonal* matrix that should be
trivially invertible.

Does anyone know why Inverse has catastrophically failed here?




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