My cousin. Math in the first grade is average, but I am a little tired of learning and my grades are not very high. During the winter vacation, I took him to preview the content of next semester. The Pythagorean Theorem taught to him at that time seemed to stimulate his interest in mathematics. He thinks about it every day when he eats and sleeps. The first thing that surprised me was that I was lying in bed at night and worked out the ratio of the height to the side length of a regular tetrahedron. I still remember clearly that it was two-thirds under the root sign. Later, I will go to my high school math and physics table, and only one Pythagorean theorem proves the above Helen formula, triangle circumscribed circle formula and so on. So I got full marks at the end of the first semester of mathematics, and my aunt praised me for my good winter vacation counseling. After that, I began to learn trigonometric functions, similar triangles and so on. By looking up the dictionary, I then proved the addition and subtraction formula, multiplication and difference, multiplication and difference, general formula and so on of trigonometric function. In my own understanding. I have always been good at math in high school, but trigonometry is definitely not as good as him. I'm going to let him take part in a math competition in grade three, but he was fascinated by relativity, quantum mechanics and so on when he watched the science and education channel. He pestered me to tell him these things every summer. Later, I gave him a copy of Hawking's A Brief History of Time, and the math competition was dropped. But he did win the second prize in the physics competition in high school, which was quite right for the book I gave him.