Liu Hui, a great mathematician in Wei and Jin Dynasties, got the approximate value of π only by connecting a regular polygon in a circle, and also got the π value accurate to two decimal places. His method was later called cyclodialysis. He used the secant method until a regular polygon of 192 was connected to the circle.

Zu Chongzhi, a mathematician in the Northern and Southern Dynasties, further got the π value accurate to 7 decimal places (about the second half of the 5th century).

However, it was not until 1573 that the West was studied by German Otto. He calculated pi between 3. 14 15926 and 3. 14 15927, becoming the first scientist in the world to calculate pi to more than seven figures.

In the pre-Qin period, there were records of "counting officials", "tying ropes" and "carving wood" in China. Although there are some legends, it shows that people have realized this. Legend has it that Fuxi also created "rules" and "moments".

Since people have the concept of number, they have begun to distinguish how much, and created the symbol of counting.

Oracle Bone Inscriptions (BC 14-BC 1 1 century) has 13 numbers, of which the largest number is "30,000" and the smallest is "one". One, ten, a hundred, a thousand, ten thousand, each with a proper name. It already contains the bud of decimal position value system. It is said that Fuxi created the "rules" of drawing circles and the "moments" of drawing edges. It is also said that Chu, the courtier of the Yellow Emperor, was the founder of "rules" and "norms". As early as when Dayu was in charge of water conservancy, Yu was a "left-handed" (holding a ruler in his left hand) and a "right-handed" (Historical Records of Yu Benji). Therefore, we can say that "rules", "moments", "accuracy" and "ropes" were the earliest mathematical tools used by our ancestors. People need mathematical knowledge to measure the land area, calculate the height and depth of mountains and valleys, calculate the yield, exchange millet and make calendars.

At the end of the Spring and Autumn Period, people have mastered the complete decimal notation, and this advanced calculation tool is widely used. People are already familiar with the multiplication table of 1999, four integer operations and used fractions.

After the Ming dynasty, abacus was spread all over the world, and many varieties appeared. But it is not as popular as people think. The earliest calculation tool in the west is the slide rule invented by Gunter, an Englishman, in 162 1 year.