matrix problem

Discussion in 'Homework Help' started by ees1, Oct 16, 2008.

  1. ees1

    Thread Starter Active Member

    Jan 7, 2008
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    One of my lecture notes showing a 3x3 matrix, let's name this matrix Y.
    I am confused about the result Y^-1.
    I am trying to find some study material for relating to Y^-1, and I couldn't find any useful information(actually I still don't know how professor got his answer)
    I guess the material I studied wasn't right. Could anyone can provide the searching key words for learning this related subject?
     
  2. Papabravo

    Expert

    Feb 24, 2006
    10,138
    1,786
    Sure, Y^-1 is the inverse of Y. When you multiply the two matricies together you get the Identity matrix
    Code ( (Unknown Language)):
    1.  
    2. Y*Y^-1 = I = [ 1 0 0 ; 0 1 0 ; 0 0 1]
    3.  
    Many software packages like Matlab, Scilab, and R will give you the inverse of a 3 x 3 matrix in the twinkling of an eye. I've heard tell that inverting one by hand is possible by using minors and cofactors but I haven't done it recently. Inverting a 4 x 4 or larger is definitely not -- you'll excuse the expression -- a hand job.
     
  3. ees1

    Thread Starter Active Member

    Jan 7, 2008
    37
    0
    thank you. I think I will use the TI caculator instead.:)
     
  4. scubasteve_911

    Senior Member

    Dec 27, 2007
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  5. Dave

    Retired Moderator

    Nov 17, 2003
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    PB, I recall the manual approach was quite laborious. You are right to suggest numerical packages like Matlab, which is expensive, so look at one of the matrix-based (free) alternatives: http://forum.allaboutcircuits.com/blog.php?b=65

    Dave
     
  6. Papabravo

    Expert

    Feb 24, 2006
    10,138
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  7. Dave

    Retired Moderator

    Nov 17, 2003
    6,960
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    Added to the list. Thanks Papabravo.

    Dave
     
  8. hgmjr

    Moderator

    Jan 28, 2005
    9,030
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    Don't overlook the fact that Microsoft EXCEL has a matrix function that can be used to perform matrix manipulation.

    hgmjr
     
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