1. In the analysis, π can be strictly defined as the smallest positive real number x satisfying sin x = 0. Pi is expressed in letters (pronounced pài) and is a constant (approximately equal to 3. 14 1592654), indicating 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 1592654 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.
Second, pai has multiple meanings, as follows:
1, pai is pi.
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.
2. Pie belongs to music: beat.
Shoot a low-frequency variable-amplitude sound composed of two sounds with similar frequencies. Common jumping phenomena are: when the generator is started, the bell obviously fluctuates and the magnet hums. In forced vibration, beat phenomenon can also be observed when the frequency of excitation function is close to the frequency of vibration system.
3.pai is an e-commerce term: taking pictures.
Photographing refers to the process from purchasing goods to payment to trading platform. Taking pictures of the baby means that the front part of the sales contract has been signed. Next, if you have freight or anything that needs to be modified by the seller, please ask the seller to modify it. The seller will inform you that it has been revised.
Formula related to circle:
1, area of semicircle: s semicircle = (π r 2)/2. (r is the radius).
2. The area of the circular ring: s great circle -S small circle = π (r 2-r 2) (r is the radius of the great circle and r is the radius of the small circle).
3. Circumference: C=2πr or c = π d..(d is the diameter and r is the radius).
4. The circumference of a semicircle: d+(πd)/2 or d+π r (d is the diameter and r is the radius).
5. Sector arc length L= central angle (arc system) ×R= nπR/ 180(θ is central angle) (r is sector radius).
6. Sector area S=nπ R_/360=LR/2(L is the arc length of the sector).
7. The radius of the cone bottom surface r=nR/360(r is the radius of the bottom surface) (n is the central angle).
In the sum of infinite small sector areas, so in the last formula, the sum of small arcs is the circumference of a circle, so there is S=πr_.