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Re: expression form

  • To: mathgroup at
  • Subject: [mg101014] Re: [mg100997] expression form
  • From: "Scot T. Martin" <smartin at>
  • Date: Sat, 20 Jun 2009 04:03:26 -0400 (EDT)
  • References: <>

I get a different result:

In[1]:= a={a1,a2,a3};P={{p11,p12,p13},{p21,p22,p23},{p31,p32,p33}};

In[2]:= a.P.a

Out[2]= a1 (a1 p11+a2 p21+a3 p31)+a2 (a1 p12+a2 p22+a3 p32)+a3 (a1 p13+a2 
p23+a3 p33)

On Fri, 19 Jun 2009, Haibo Min wrote:

> Hi, I am fairly new to mathematica, and I have a question on the matrix
> multiplication operator.
> Suppose a={a1,a2,a3},P={{p11,p12,p13},{p21,p22,p23},{p31,p32,p33}}. I want
> to get the explicit expression of a'Pa, where a' is the transpose of vector
> a. Since there is no "transpose" concept for vector, my expression in
> mathematica is
> a.P.a
> However, it just
> returns  {a1,a2,a3}.{{p11,p12,p13},{p21,p22,p23},{p31,p32,p33}}.{a1,a2,a3},
> seems nothing is done about this, why?
> I use mathematica v7.0
> Thank you!
> Haibo Min
> yshdfeng at

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