What are the interesting popular science knowledge in mathematics?

Interesting math science tips are as follows:

I. Arabic numerals

Arabic numerals were invented by ancient Indians and later spread to Arabia and Europe. Europeans mistakenly thought it was invented by Arabs, so they called it "Arabic numerals". Because it has been circulated for many years, people call it Yi, so people still mistakenly believe that these numerical symbols invented by ancient Indians are called Arabic numerals.

Second, 99 songs

Jiujiuge is the multiplication formula we use now. As early as the Spring and Autumn Period and the Warring States Period BC, Jiujiu songs have been widely used by people. In many works at that time, there were records about Jiujiu songs. The original 99 songs started from "99.8 1" to "22.24", with 36 sentences. Because it started with "998 1", it was named 99 Song.

The expansion of Jiujiu Song to "One for One" was between the 5th century and10th century. It was in the 13 and 14 centuries that the order of Jiujiu songs became the same as it is now, from "one for one" to "9981". At present, there are two kinds of multiplication formulas used in China. One is a 45-sentence formula, usually called "Xiao Jiujiu"; There is also a sentence 8 1, which is usually called "Big Uncle Nine".

Third, Mobius ring

Mobius ring is a topological structure with only one face and one boundary. You can twist a piece of paper into 180 degrees, and then stick the two ends together to form a Mobius ring.

Cutting Mobius ring along the midline can get a larger ring for the first time. The second time and after, you will get two nested rings every time. The middle will never break, which is also the magic of Mobius ring.

Four, Klein bottle

1882, the famous mathematician Felix Klein discovered the famous "bottle" named after him: Klein bottle. Klein bottles are like bottles, but they have no bottom. Its bottleneck is elongated, then it seems to pass through the bottle wall, and finally the bottleneck is connected with the bottom ring. Interestingly, if you cut the Klein bottle along its symmetry line, you will get two Mobius rings.

Fifth, the golden section.

The golden section was put forward 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.