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 area of a circle to the square of its radius. 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 satisfaction crime? x？ The smallest positive real number x = 0.

Pi in Greek letters? π (pronounced pài) is a constant (approximately equal to 3. 14 1592654), which 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. 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.

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.

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International pi day:

20 1 1 year, the International Mathematical Association officially announced that March 14 every year would be designated as the International Mathematics Festival, which originated from the pi of Zu Chongzhi, an ancient mathematician in China. ?

Pi day can be traced back to1March, 98814th, a physicist at the Science Museum in San Francisco, Larry Shaw. He organized museum employees and participants to make 3 and 1/7 laps around the museum monument (22/7, one of the approximations of π) and eat fruit pies together. Later, the San Francisco Science Museum inherited this tradition and held a celebration on this day every year.

In 2009, the US House of Representatives formally passed a non-binding resolution, which designated March 14 as "pi day" every year. The resolution holds that "since mathematics and natural science are interesting and indispensable parts of education.

Learning π is an interesting way to teach children geometry and attract them to study natural science and mathematics ... π is about 3. 14, so March 14 is the most suitable day to commemorate pi day. "

Reference: Baidu Encyclopedia -Pi