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Re: Mathematica bug??

  • To: mathgroup at smc.vnet.net
  • Subject: [mg100556] Re: [mg100540] Mathematica bug??
  • From: "Matthias Bode" <lvsaba at hotmail.com>
  • Date: Mon, 8 Jun 2009 02:04:50 -0400 (EDT)
  • References: <200906070902.FAA28100@smc.vnet.net>

Hello:

In[1]:=
Inverse[{{Sqrt[1 - 2/r], 0, 0, 0}, {0, 1/Sqrt[1 - 2/r],
    0, 0}, {0, 0, r, 0}, {0, 0, 0, r*Sin[teta]}}]

Out[1]=
{{1/Sqrt[1 - 2/r], 0, 0, 0}, {0, Sqrt[1 - 2/r], 0, 0},
  {0, 0, 1/r, 0}, {0, 0, 0, Csc[teta]/r}}

In[2]:=
{{1/Sqrt[1 - 2/r], 0, 0, 0}, {0, Sqrt[1 - 2/r], 0, 0},
   {0, 0, 1/r, 0}, {0, 0, 0, Csc[teta]/r}} .
  {{Sqrt[1 - 2/r], 0, 0, 0}, {0, 1/Sqrt[1 - 2/r], 0, 0},
   {0, 0, r, 0}, {0, 0, 0, r*Sin[teta]}}

Out[2]=
{{1, 0, 0, 0}, {0, 1, 0, 0}, {0, 0, 1, 0}, {0, 0, 0, 1}}

does work as expected.

Best regards,

MATTHIAS BODE
Las Lomas de Aranjuez
COCHABAMBA/BOLIVIA
S 17.35775°, W 066.14577°
2'740 m AMSL.

CEL: +591-70 71 56 64
TEL: +591-4-445 76 65
LVSABA at HOTMAIL.COM

--------------------------------------------------
From: "oshaughn" <oshaughn at gravity.psu.edu>
Sent: Sunday, June 07, 2009 9:02 AM
To: <mathgroup at smc.vnet.net>
Subject: [mg100556] [mg100540] Mathematica bug??

> {{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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