In 1650 BC, π = (4/3) 3 = 3. 1604 in the rand papyrus written by the Egyptians. However, the first scientific attempt on π should be attributed to Archimedes.
Archimedes calculated π value by inscribed and circumscribed regular polygons. Mathematically, it is generally called the classic method of computer.
In the 3rd century BC, mathematics in ancient Greece was very developed. In order to make the mathematical calculation simple, people choose a circle with the length as the diameter. The circumference of this circle is between that of any inscribed regular polygon and that of any circumscribed regular polygon. In this way, it is easy to get the upper and lower bounds of π, because it is relatively simple to calculate the finance ministers inscribed and circumscribed regular polygons. Archimedes also mastered this principle. He started with the inscribed hexagon and followed this method step by step, and got the finance ministers with 12, 24, 38 and 96 sides inscribed with regular polygons. Using this method, he finally got the π value between 223/7 1 and 22/7, which is 3. 14. This method and numerical value are published in his collection "Measurement of Circle".
In AD 150, Ptolemy, a Greek mathematician, wrote a set of mathematics. In this book, he thinks that the value of π377/ 120 is 3. 14 16. His calculation result is extracted from the string table. In his chord table, the chord length of the circle corresponding to the central angle (each angle is separated by one and a half degrees) is given. If the chord length corresponding to the central angle 1 degree is multiplied by 260 and divided by the diameter of the circle, the π value is obtained.
In fact, π has applications in nine arithmetic classics in ancient China. The formula for calculating the area of a circle is s = 3/4d2ors =112p2, where d is the diameter and p is the circumference of the circle. A.D. 130 years ago, Zhang Heng, an astronomer in the Eastern Han Dynasty, calculated that π was 3. 1622, that is, √ 10. He is the first person in the world to adopt π = √ 10. In the 3rd century, Wang Fan, a famous astronomer and mathematician in the Three Kingdoms period, took π = 142/45 or 3. 1555.
In ancient China, Liu Wei was the first person to raise the approximate value of pi to a theoretical level. He independently created "secant" and used inscribed regular polygons systematically and strictly to obtain the approximate value of pi. He calculated the area of inscribed regular hexagon 192, and got 3. 14 1024.