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Math Help - Inverting a matrix

  1. #1
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    Inverting a matrix

    a 1
    1 -a

    i find the inverse, which is

    a/(a^2 + 1) 1/(a^2 + 1)
    1/(a^2 + 1) -a/(a^2 + 1)

    which is correct, no?

    so can i multiply that matrix by (a^2 + 1) and get this matrix

    a 1
    1 -a

    which is the same as the initial matrix? so is it true that that matrix is its own inverse?


    Sorry guys but i cant seem to work out how to do matrices in here properly
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  2. #2
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    Just checking I'm following what you're after: if you call your original matrix A, and your inverse is A^-1, you want A^-1A = I?
    If so, your inverse is

    -a/(-a^2 - 1) -1/(-a^2 - 1)
    -1/(-a^2 - 1) a/(-a^2 - 1)

    If your original matrix was its own inverse, then AA=I, but in your case AA =
    a^2 + 1 0
    0 1 + a^2
    Which is (a^2 + 1)I, but not I itself.
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  3. #3
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    yeah thats right...thanks heaps mate

    i think ive worked out what i need to know now, thanks heaps
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