The recitation formula of 1 to 20 is: remember that 1π equals 3. 14, then recite 2π equals 6.28 (repeated several times), then recite 1 π plus 2 π together, then recite 3π equals 9.42 together (repeated several times), and the same π ~ 3 π together.

Application of pi

Pi is expressed by the Greek letter π (pronounced pài), which is a constant (approximately equal to 3. 14 1592653), 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. The fractional part 3. 14 1592653 is 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.

1965, 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. 20 15 scientists at the university of rochester found a formula with the same 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.