The origin of pi was a long time ago. People see that the ratio of the circumference of a circle to the straight meridian is a constant independent of the size of the circle, which is called pi. 1600, William Autolante of Britain first used pi to express pi, because pi is the first letter of "circumference" in Greek, and δ is the first letter of "diameter". When δ Pi is π. 1706. Jones in Britain first used π. 1737. Euler used π in his works. Later, it was widely accepted by mathematicians and has been used ever since. π is a very important constant. A german mathematician commented: "the accuracy of calculating pi in a country in history can be used as an important symbol to measure the level of mathematical development at that time." Many mathematicians at all times and at home and abroad are tirelessly seeking the calculation method of π value. In 200 BC, the ancient Greek mathematician Archimedes first gave the correct solution of π value in theory. He approached the circumference of a circle from both big and small directions at the same time, and skillfully calculated about 150 years before π met. Ptolemy, another ancient Greek mathematician, gave an approximate value of π by the chord table method (multiplying the chord length by 360 and dividing it by the diameter of the circle at the central angle 1). In the past 200 years, Liu Hui, a mathematician in China, provided a scientific method to find pi, which reflected this extreme view. The methods of Liu Hui and Archimedes are as follows. He only takes "internal engraving" instead of "external cutting". Using the inequality of circular area, he gets twice the result with half the effort. Then, Zu Chongzhi leads the world in the calculation of pi, and obtains the "divisor rate" and "secret rate" (also known as ancestor rate) to get 3. 14 15926.