       Re: expression form

• To: mathgroup at smc.vnet.net
• Subject: [mg101014] Re: [mg100997] expression form
• From: "Scot T. Martin" <smartin at seas.harvard.edu>
• Date: Sat, 20 Jun 2009 04:03:26 -0400 (EDT)
• References: <200906200048.UAA00953@smc.vnet.net>

```I get a different result:

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

In:= a.P.a

Out= 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},
> I use mathematica v7.0
>
> Thank you!
>
> Haibo Min
> yshdfeng at gmail.com
>
>
>

```

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