1, there is no maximum prime number. Euclid gave a beautiful and simple proof.

2. Goldbach conjecture: Any even number can be expressed as the sum of two prime numbers. Chen Jingrun's achievement is that any even number can be expressed as the sum of the products of one prime number and no more than two prime numbers.

3. Fermat's last theorem: n power of x+n power of y = n power of z, and n> has no integer solution at 2 places. Euler proofs 3 and 4, 1995 were proved by British mathematician andrew wiles.

4. The golden section was proposed by Pythagoras. Once, Pythagoras passed by the blacksmith's workshop and was fascinated by the tinkling of iron. In order to reveal the secrets of these sounds, he measured the size of the hammer and anvil and found that there was a very harmonious proportional relationship between them. After returning home, he took out a thread and divided it into two sections. After repeated comparisons, he finally decided that the ratio of 1:0.6 18 was the most beautiful. This ratio is recognized as the most aesthetic ratio, so it is called the golden section.

5. If you add two diagonal lines at both ends of a line segment and two diagonal lines at both ends of another line segment, the former is much longer than the latter. There is a theory about this illusion, which is called nerve inhibition theory.

It believes that when two contours are close to each other, the adjacent nerve groups on the retina will inhibit each other, leading to the displacement of the contours and the illusion.