## 2009-09-09

### cool matrix (4)

There are so many applications of this linear operation. For example, one day's total sales of a supermarket can be computed in the same way:

price of item 1 * number of sold of item 1 + price of item 2 * number of sold of item 2 + ...

Again, price of item 1 * price of item 2 has no meaning here and therefore, we should not do that.

Matrix is useful when we want to perform this kind of operation. Of course we can use matrix (so many) different ways, even so this is still useful.

Until here, I hope this is understandable for a junior high school student. But, I realize I could not reach the entitled theme, a cool matrix, in this pace. Then, I will skip several topics, like, what is the relationship between a linear operation and a matrix. I am going to talk about a cool matrix in the next article. The audience would be a bit limited. I assume you know what is matrix or vector and how to write down this language, also can speak a bit. So I assume the audience is a
high school student or more.