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.
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.
Pi:
Later mathematicians tried to work out the specific value of π. Mathematician Liu Hui used the secant method, that is, the circumference of a circle inscribed with a regular polygon and circumscribed with a regular polygon is close to the circumference of a circle, and the circle is close to a 192 polygon with a pi of about 3. 14.
The general method of cutting circle is found in middle school mathematics textbooks. But it must be noted that, to a great extent, it is only a method to calculate pi, and it seems to be a fact that pi is C = π * d, and this method is only to determine the value of π. If you think about it carefully, you will know that this is problematic, because they have not logically proved that the circumference of a circle is really proportional to the diameter. Furthermore, their concept of circumference is only intuitive and irrational.