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Re: expression form

  • To: mathgroup at smc.vnet.net
  • Subject: [mg101010] Re: [mg100997] expression form
  • From: "David Park" <djmpark at comcast.net>
  • Date: Sat, 20 Jun 2009 04:02:42 -0400 (EDT)
  • References: <33011425.1245459207888.JavaMail.root@n11>

It works for me.

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

a.P.a

Giving...

a1 (a1 p11 + a2 p21 + a3 p31) + a2 (a1 p12 + a2 p22 + a3 p32) + 
 a3 (a1 p13 + a2 p23 + a3 p33)

Copy and paste and try it again. Maybe you didn't type in the expression you
thought you did.


David Park
djmpark at comcast.net
http://home.comcast.net/~djmpark/  



From: Haibo Min [mailto:yshdfeng at gmail.com] 
Sent: Friday, June 19, 2009 8:48 PM


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 gmail.com





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