Brief introduction of pi
It is the ratio of the circumference to the diameter of a circle, generally expressed by the Greek letter π, and is a common 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 number x satisfying sinx=0.
Pi is written in the Greek letter π (pronounced [pa? ]), which is a constant (approximately equal to 3. 14 1592654), is 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. 3. The nine decimal places of141592654 are enough for general calculation.
Even if engineers or physicists want to make more accurate calculations, they only need to take the values to a few hundred decimal places at best. 1665, the British mathematician john wallis published a mathematical monograph, in which he derived a formula and found that pi is equal to the product of infinite fractions.
In 20 15, scientists from the university of rochester found the same formula of pi in the quantum mechanical calculation of hydrogen atomic energy level. On March 4th, 20 19, Google announced that pi has now reached 3 1.4 trillion digits after the decimal point.