Zu Chongzhi word Wen Yuan, originally from Kuai County, Xiangyang (now Laiyuan County, Hebei Province), moved to Jiangnan to escape the war in the north. He was born in a scholar-bureaucrat family, and his father and grandfather were very good at astronomy and calendar. Influenced by his family, Zu Chongzhi loved science from an early age. As an adult, Zu Chongzhi decided to devote himself to the study of pi and calculate it more accurately.
Circle is the most common geometric figure in nature, and many objects are round. But how to calculate the circumference and area of a circle? The ancients conducted research and exploration very early. The ancients found that the ratio of the circumference to the diameter of a circle is a constant, which is called pi. If pi can be accurately calculated, and then the length of the diameter is measured with a ruler, the circumference and area of the circle can be easily calculated. What exactly is pi? In ancient China, there was an arithmetic book called Zhouyi Shu Jing, which was one of China's earliest mathematical works. The concept of "three times a week" put forward in the book, which is called the ancient rate, is of course too rough. The value of pi calculated by Liu Xin at the end of Han Dynasty was 3. 1547. The pi calculated by Zhang Heng in the Eastern Han Dynasty was 3. 1622. At the end of the Three Kingdoms, Liu Hui created the secant with the idea of limit, and calculated the perimeter and area of the inscribed regular polygon 192, and got the pi of 3. 14. Later, he calculated the perimeter and area of the 3072 polygon inscribed in the circle, and got the pi of 3.1416 (3927/1250).
Zu Chongzhi thinks that these calculation results of predecessors are still too rough and have great errors. However, he did not despise the previous research results, but seriously studied and thought about their research methods. Later, on the basis of previous research results, he innovated the calculation method of pi, which was named "suffix" Using this method, Zu Chongzhi accurately calculated pi from 3. 14 15926 to 3. 14 15927, and used two fractional values: 22/7 (sparsity) and 355/1. This was the most advanced pi in the world at that time. In the west, it was not until 1573 that German Otto calculated pi more accurately, which was more than 1 100 years later than Zu Chongzhi.
After Zu Chongzhi accurately calculated the last seven digits of pi, he quickly put it into practice. He himself used his pi to study the problem of weights and measures and used it to evaluate the calculation of ancient measuring instruments. The jade bucket made in the first year of Emperor Wudi's treasure in the Northern Zhou Dynasty (AD 56 1) was calculated with pi of 3. 14 15926. Zu Chongzhi wrote his own research results into a book "Editing Books". During the Sui and Tang Dynasties, seal script has always been one of the basic contents of mathematics education. Unfortunately, this book was later lost because of the war, which is a great loss in the history of Chinese mathematics.