Proof About MatricesDate: 06/02/99 at 00:46:48 From: Ryuhei Hagiwara Subject: Matrices How do I prove that in two 2 x 2 matrices, A and B, AB - BA will never be the multiplication identity matrix? Date: 06/02/99 at 12:17:24 From: Doctor Rob Subject: Re: Matrices One way is to show that the main diagonal entries of the result are the negatives of each other. Another way of saying this is that the trace of the result is zero, because tr(X-Y) = tr(X) - tr(Y) and tr(AB) = tr(BA). - Doctor Rob, The Math Forum http://mathforum.org/dr.math/ |
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