What method is used to calculate pi?

Pi is one of the important constants in mathematics. It refers to a mathematical constant representing the ratio of the circumference to the diameter of a circle, which is expressed by the Greek letter π. π is also equal to the ratio of the square of the area and radius of a circle, and the approximate value is about 3. 14 159265359, which is the key value for accurately calculating the geometric shapes such as the circumference of a circle, the area of a circle and the volume of a sphere. So how is pi calculated? Let's take a look with Bian Xiao!

The earliest written records about π came from Babylonians around 2000 BC, who thought π=3. 125, while the ancient Egyptians used π=3. 1605. There is a record in China's ancient books that "the diameter of a circle is one and three", that is, π=3, which is also the π value recorded in the Old Testament. We can find π≈3. 1622 in the classic of Jainism in ancient India. These early π values are generally estimated by measuring the circumference of a circle, then measuring the diameter of the circle and dividing it. Because at that time, the circumference of a circle could not be accurately measured, and of course it was impossible to get an accurate π value through estimation.

Coincidentally, Liu Hui, a mathematician in China during the Three Kingdoms period, also gave a similar algorithm in 264 AD when commenting on Nine Chapters Arithmetic, and called it the method of cutting circles. The difference is that Liu Hui calculates pi by gradually approaching the area of a circle with the area of a regular polygon inscribed in the circle. About 480 AD, Zu Chongzhi, a great scientist in the Southern and Northern Dynasties, calculated 3. 14 15926.