Who can talk about the geometric meaning of matrix multiplication? The more popular the better.

Geometric shapes can be represented by vector groups (such as a set of vertices) in space.

The transformation can also be represented by a square matrix,

For example, expand, contract, rotate, translate geometry, etc.

c=ab，

That is, c is the result of b transformation of vector group a,

The inverse transformation of b transformation is the inverse matrix of b,

A = CB (- 1) Change it back. If B is irreversible, the transformation is said to be irreversible.

Such as projection transformation.

For example, the rotation formula matrix of a two-dimensional plane is t=[cos(phi)

sin(φ)/-sin(φ)

cos(phi)]

("/"indicates the next line)

Then put the vector [x]

/

y]，

The angle of turning φ counterclockwise can be expressed as:

[x '

/

y']=t[x

/

y]

The course of cad/cam will be introduced in detail.