[tptacek]

What graphical illustration do you think this is missing? How would that make things better? Have you ever seen http://matrixmultiplication.xyz/? Great graphical illustration. Also: a really unhelpful way to understand matrix multiplication.

This is part 2 of a series, all under the same name; the first part is extensively illustrated (and I'm not sure the part 1 illustrations are all that helpful).

[MaxBarraclough]

I agree that's a poor way to teach matrix multiplication. This topic arose last year. [0]

Don't introduce any clumsy nonstandard transformations like 'rotating' a matrix, just highlight the relevant row and column. [1]

[0] https://news.ycombinator.com/item?id=41402224

[1] https://www.mathsisfun.com/algebra/images/matrix-multiply-a.... (from https://www.mathsisfun.com/algebra/matrix-multiplying.html )

[tptacek]

I kind of hate all these, because matrix multiplication is easiest to think of as simply repeated matrix-vector multiplication, which you need anyways (and earlier).

[griffzhowl]

Illustrating the dot product using the projection of one vector on another conveys the geometric idea. Then it's transparent why "orthogonal" means dot product = 0.

The author seems to be taking a different tack though, and maybe doesn't want to be too tied to this particular geometric picture