Talk:Matrix multiplication

A good way to envisage matrix mult is to split the first into rows, the 2nd into columns, and vector dot-produc them.

Matrix multiplication can also be envisages a dot products of vectors. The above example becomes::

{\begin{bmatrix}\mathbf {a} _{1}\\\mathbf {a} _{2}\end{bmatrix}}*{\begin{bmatrix}\mathbf {b} _{1}&\mathbf {b} _{2}\end{bmatrix}}={\begin{bmatrix}\mathbf {a} _{1}\cdot \mathbf {b} _{1}&\mathbf {a} _{1}\cdot \mathbf {b} _{2}\\\mathbf {a} _{2}\cdot \mathbf {b} _{1}&\mathbf {a} _{2}\cdot \mathbf {b} _{2}\end{bmatrix}}

The above is for the article, but trying to get the numbers right makes my brain ache. I'm leaving it here in case I've got them wrong. -- Tarquin 17:30 Jan 15, 2003 (UTC)

Perhaps it is good to work with column vectors; then the a's on the left must get a T for transposed. - Patrick 17:39 Jan 15, 2003 (UTC)

yup, that's the right way to do it.

Okay, here's something that is probably one of these things that only makes sense to me.

it basically shows that the entries of the product matrix are filled in according to which row and column are multiplied. If anyone else gets it & thinks it useful for the article , please add it -- Tarquin 23:46 Jan 21, 2003 (UTC)

(except I've just realised the result matrix in the pic has the wrong number of rows .... hmmmmm. if there's a call for it I'll remake it)

Surely it makes sense to me also! This diagram uses unequal m and p, which is better (more general). I would use the diagram and add a third column for B in the example. - Patrick 01:14 Jan 22, 2003 (UTC)