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Pi is the ratio of the circumference to the diameter of a circle, which is generally expressed by the Greek letter π and is a universal mathematical constant in mathematics and physics. π is also equal to the ratio of the square of the area and radius of a circle, which is the key value to accurately calculate the geometric shapes such as the circumference of a circle, the area of a circle and the volume of a ball. In the analysis, π can be strictly defined as the smallest positive real number x satisfying sinx=0.

Pi is written in the Greek letter π (pronounced [pa? ]), which is a constant (approximately equal to 3. 14 1592653), is the ratio of circumference to diameter. It is an irrational number, that is, an infinite cycle decimal.

The origin of pi:

An ancient Babylonian stone tablet (about BC 1900 to BC 1600) clearly recorded that pi = 25/8 = 3. 125. Rhind papyrus, an ancient Egyptian cultural relic of the same period, also shows that pi is equal to the square of score 16/9, which is about 3. 1605.

Egyptians seem to have known pi earlier. British writer john tyler (1781–1864) wrote in his masterpiece The Great Pyramid: Why was it built and who built it? ) It is pointed out that the pyramid of khufu built around 2500 BC is related to pi.

For example, the ratio of the circumference to the height of a pyramid is equal to twice the pi, which is exactly equal to the ratio of the circumference to the radius of a circle. The Brahman of Sa tabata, an ancient Indian religious masterpiece written from 800 to 600 BC, shows that pi is equal to 339/ 108, which is about 3. 139.