The origin of pi 3. 14 is easy to understand. What is the formula?

China, who first recorded that "the path is three times a week" in Zhou suan Jing, took the value of π as 3. In Wei and Jin Dynasties, Liu Hui approached the circumference (i.e., "secant circle") by gradually increasing the number of sides of a regular polygon, and got the approximate value of π 3. 14 16.

Zhang Heng of Han Dynasty concluded that π divided by the square of 16 equals 5/8, that is, π equals the root of 10 (about 3. 162). Although this value is not accurate, it is easy to understand, so it has been popular in Asia for some time. Wang Fan (229-267) discovered another value of pi, that is, Zu Chongzhi and his son calculated the pi of a polygon with 24,576 sides, which is about 355/ 1 13. Compared with the real value, the error is less than one in eight hundred million. This record was not broken until 1000 years later.