200906Japan 3.6(night)-4.6

3.6 Night

Night, I met my friend G. He is now famous and gets inviatation letters from internatonal film festivals. I always complained ``I don't understand what is this article.'' But, he always try to explain how it is nice. Recently, I started to understand some of them. Just feel something. This is stereo shadow. This is fun. (picture)

By the way, when I was a student, I bought a theater ticket. I felt that was unique, but, I did not understand it. Then I asked them after the play. Then the director answered, ``What? How impolite you are. How can't you understand my play?'' After few years, I lost the trail of her theatrical company. If you make a sincere question, and the answer was ``How impolite you are.'' Then you made a right question, I believe. The responders need to deceive the question since they cannot answer the question or answering question negates them.

I believe both research and software development are based oncommunication. Maybe artistics activity is also based on communication. I want to tell something, I want to show something, but always ``to someone.''

We watched Blade Runner togather again.

4.6

Morning, I visited old friends and they are now parents. We learn Aikido together. Their child has a lot of imagination and so many vocabulary. Yes, the mother's field was literature. I think the most important ability is natural language (mother tongue). Especially if the person goes to science or mathematics area. Because the first task of science is to understand what is the problem, that is given by the natural language. Then if one has an answer, s/he need to explain it to people.

Night, I met a sister of my colleague. I never met such a person who can read/write almost perfect Japanese, but a German person. She told me about her life a bit and it seems there was a lot of luck she had. But I see it is based on calculated strategy. I have met several people, who want to visit to Japan and want to live there. But, she can read and write Japanese. This does not belong to luck. Some says like her, "I'm interested in business. Maybe I join a foreign company in Japan."But she is writing doctor thesis about the role of foreign companies in Japan, and contacted managers of such companies. That's not luck again. This is strategy. She is not only intelligent, but also an attractive woman.

Comments

Why A^{T}A is invertible? (2) Linear Algebra

Why A^{T}A has the inverse Let me explain why A^{T}A has the inverse, if the columns of A are independent. First, if a matrix is n by n, and all the columns are independent, then this is a square full rank matrix. Therefore, there is the inverse. So, the problem is when A is a m by n, rectangle matrix. Strang's explanation is based on null space. Null space and column space are the fundamental of the linear algebra. This explanation is simple and clear. However, when I was a University student, I did not recall the explanation of the null space in my linear algebra class. Maybe I was careless. I regret that... Explanation based on null space This explanation is based on Strang's book. Column space and null space are the main characters. Let's start with this explanation. Assume x where x is in the null space of A . The matrices ( A^{T} A ) and A share the null space as the following: This means, if x is in the null space of A , x is also in the null spa

Gauss's quote for positive, negative, and imaginary number

Recently I watched the following great videos about imaginary numbers by Welch Labs. https://youtu.be/T647CGsuOVU?list=PLiaHhY2iBX9g6KIvZ_703G3KJXapKkNaF I like this article about naming of math by Kalid Azad. https://betterexplained.com/articles/learning-tip-idea-name/ Both articles mentioned about Gauss, who suggested to use other names of positive, negative, and imaginary numbers. Gauss wrote these names are wrong and that is one of the reason people didn't get why negative times negative is positive, or, pure positive imaginary times pure positive imaginary is negative real number. I made a few videos about explaining why -1 * -1 = +1, too. Explanation: why -1 * -1 = +1 by pattern https://youtu.be/uD7JRdAzKP8 Explanation: why -1 * -1 = +1 by climbing a mountain https://youtu.be/uD7JRdAzKP8 But actually Gauss's insight is much powerful. The original is in the Gauß, Werke, Bd. 2, S. 178 . Hätte man +1, -1, √-1) nicht positiv, negative, imaginäre (oder gar um

Why parallelogram area is |ad-bc|?

Here is my question. The area of parallelogram is the difference of these two rectangles (red rectangle - blue rectangle). This is not intuitive for me. If you also think it is not so intuitive, you might interested in my slides. I try to explain this for hight school students. Slides: A bit intuitive (for me) explanation of area of parallelogram (to my site, external link) .

Lx=d: SundayResearch

Search This Blog