Pi, generally expressed by π, is a common mathematical constant in mathematics and physics. It is defined as the ratio of the circumference to the diameter of a circle. Its pi is also equal to that ratio of the area of a circle to the square of its radiu. Accurate calculation of geometric shapes such as circle perimeter, circle area and sphere volume is the key value. In the analysis, π can be strictly defined as the smallest positive real number x satisfying sin(x) = 0. In June of 20 1 1 year, some scholars thought that the definition of pi was unreasonable and asked to change it to 6.28.

Pi (π reading pài) is a constant (approximately equal to 3. 14), representing the ratio of circumference to diameter. It is an irrational number, that is, an infinite cycle decimal. In daily life, pi is usually expressed as 3. 14, which is used for approximate calculation. Even if engineers or physicists want to make more accurate calculations, they only take values to about 20 decimal places.

π (pronounced "Pi") is the 6th Greek letter/kloc-0, which has nothing to do with pi, but the great mathematician Euler has used π in letters and papers since 1736. Because he is a great mathematician, people have followed suit and used pi to express pi. But π can be used to represent something other than pi, which can also be seen in statistics. π=Pai(π=Pi) Euclid's Elements of Geometry (about the beginning of the 3rd century BC) in ancient Greece mentioned that pi was constant, and China's ancient arithmetic book Zhouyi Shu Jing (about the 2nd century BC) recorded that pi was constant.

Many approximations of pi have been used in history, most of which were obtained by experiments in the early days. For example, in ancient Egyptian papyrus (about 1700 BC), take pi = (4/3) 4 ≒ 3. 1604. The first person to find pi scientifically was Archimedes. In The Measurement of a Circle (3rd century BC), he determined the upper and lower bounds of the circumference of a circle by using the circumference of a regular polygon inscribed and circumscribed by the circle. Starting with a regular hexagon, he multiplied it by a regular 96-hexagon and got (3+( 10/7 1)).

When Liu Hui, a mathematician in China, annotated Nine Chapters Arithmetic (263), he got the approximate value of π only by inscribing a regular polygon into a circle, and also got the value of π accurate to two decimal places. His method is called the secant circle method by later generations. He used the method of secant circle until the circle inscribed the regular polygon of 192, and got the π ≈ radical sign of 10 (about 3. 14).

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