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## #1 2013-04-29 03:05:49

genericname
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### Matrix chain multiplication question

Let's say for example,
Matrices A1;A2;A3 with dimensions:

A1 = 5x10
A2 = 10x3
A3 = 3x10

Would M[2,3] be equal to (10*3*10) or (10*3)?

## #2 2013-04-29 04:24:09

bobbym

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### Re: Matrix chain multiplication question

Hi;

Okay I got the definitions of your 3 matrices.

What is M[2,3]?

You want the dimensions of A1 x A2 x A3?

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.

## #3 2013-04-30 05:11:25

genericname
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### Re: Matrix chain multiplication question

Dimensions A2 x A3. Sorry.

## #4 2013-04-30 05:19:22

bobbym

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### Re: Matrix chain multiplication question

Hi;

That would yield a 10 x 10

The number of columns of the 1st matrix must equal the number of rows of the 2nd matrix.
And the result will have the same number of rows as the 1st matrix, and the same number of columns as the 2nd matrix.

http://www.mathsisfun.com/algebra/matri … lying.html

In mathematics, you don't understand things. You just get used to them.
I have the result, but I do not yet know how to get it.
All physicists, and a good many quite respectable mathematicians are contemptuous about proof.