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Operator Algebra

  1. Mar 22, 2010 #1
    I hope someone can help me with this:

    Let the the inverse [tex]A A^{-1}=A^{-1} A=I[/tex], where I is the identity operator. Proofing that [tex](AB)^{-1}=B^{-1} A^{-1}[/tex] :

    "First, you want to check whether [tex](AB)(B^{-1} A^{-1})=I[/tex]. "

    However that means the inverse of AB multiplied by AB gives the identity operator, which isn't true, surely, due to Cramer's rule?
  2. jcsd
  3. Mar 23, 2010 #2


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    It is. That's just the definition of "inverse".
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