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Re: Multiplication of matrices

  • To: mathgroup at
  • Subject: [mg102293] Re: Multiplication of matrices
  • From: O <kakabomba at>
  • Date: Tue, 4 Aug 2009 04:28:56 -0400 (EDT)
  • References: <h4rpe1$l70$>

On Jul 30, 2:33 am, "Qing" <Qing.Zhan... at> wrote:
> Hi:
> I have two 2x2 matrices , X and Y (x, y are the inverses resp.). I need to evaluate the following expression:
> Simplify[Tr[
> X.Y.x.Y.x.y.X.y.X.y.x.Y.x.Y.X.y.X.y.X.Y.x.Y.x.Y.X.y.X.y.x.Y.x.Y.x.y.X.y.X.\
> y.x.Y.x.Y.X.y.X.y.X.Y.x.Y.x.y.X.y.X.y.x.Y.x.Y.x.y.X.y.X.Y.x.Y.x.Y.X.y.X.y]]
> but for some reason, mathematica can't do it and I need to break it into the following form:
> Clear[U1, U2, U3, U3, U4, U]
> U1 = Simplify[X.Y.x.Y.x.y.X.y.X.y.x.Y.x.Y.X.y.X];
> U2 = Simplify[y.X.Y.x.Y.x.Y.X.y.X.y.x.Y.x.Y.x.y.X.y];
> U3 = Simplify[X.y.x.Y.x.Y.X.y.X.y.X.Y.x.Y.x.y.X.y.X.y.x];
> U4 = Simplify[Y.x.Y.x.y.X.y.X.Y.x.Y.x.Y.X.y.X.y];
> U = Simplify[U1.U2.U3.U4];
> Simplify[Tr[U]]
> I have hundreds of such expression to evaluate, it is time-consuming if I break every expression by hand. Is there anyone who knows how to write a function to do this sort of task?
> Hopefully you understand my question.
> Thanks a lot.
> Qing

there are nay rule in dividing product into four parts?
there any rule in full sequence


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