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RE: Possible Bug in Mathematica 6

• To: mathgroup at smc.vnet.net
• Subject: [mg90185] RE: Possible Bug in Mathematica 6
• From: "Amir Ahmed Ansari" <aansari at softpak.com>
• Date: Wed, 2 Jul 2008 05:26:43 -0400 (EDT)

Just read your welcome mail in detail :-) I had actually already posted the
'bug' to Wolfram. They have given me the identification number [TS 21827].
So I hope you will post my email on the mailing list/newsgroup.

Thanks,

- Amir

-----Original Message-----
From: Amir Ahmed Ansari [mailto:aansari at softpak.com]
Sent: Tuesday, July 01, 2008 4:00 PM
To: 'mathgroup at smc.vnet.net'
Subject: [mg90185] Possible Bug in Mathematica 6

Hi,

I tried this on a friend=92s computer using Mathematica 6. Consider the
following matrix:

{
    { f_11, f_12, f_13, 0, 0, 0, 0, 0, 0 },
    { 0, 0, 0, f_21, f_22, f_23, 0, 0, 0 },
    { 0, 0, 0, 0, 0, 0, ( a f_11 + b f_21 ), ( a f_12 + b f_22 ), ( a f_13 +
b f_23 ) },
    { f_21, f_22, f_23, f_11, f_12, f_13, 0, 0, 0 },
    { ( a f_11 + b f_21 ), ( a f_12 + b f_22 ), ( a f_13 + b f_23 ), 0, 0,
0, f_11, f_12, f_13 },
    { 0, 0, 0, ( a f_11 + b f_21 ), ( a f_12 + b f_22 ), ( a f_13 + b f_23
), f_21, f_22, f_23 }
}


All 5x5 have a determinant of 0 as can be seen by using Det[]. Yet,
MatrixRank[] comes out to be 5. Is this a bug or am I doing something
stupid?