How to calculate the circumference of a circle?

The formula of the circumference of a circle: c = 2 π r = π d. In the formula, r is the radius of the circle and d is the diameter of the circle. Experience shows that there is a constant ratio between the circumference of a circle and its diameter, and this constant is called pi.

How to calculate the circumference of a circle

Circumference = π× diameter

c=πd

Circumference =π×2× radius

c=2πr

1. A point set whose distance from a fixed point is equal to a fixed length is called a circle. This fixed point is called the center of the circle and is usually represented by the letter "O".

2. The straight line connecting the center of the circle and any point on the circumference is called radius, which is usually represented by the letter "R".

3. The line segment with two ends on the circumference passing through the center of the circle is called the diameter, which is usually represented by the letter "D".

What is pi?

Mathematicians try to work out the specific value of π. Mathematician Liu Hui uses the secant method, that is, the circumference of a circle inscribed with a regular polygon and circumscribed with a regular polygon approaches the circumference of a circle, and the circle approaches a 192 polygon, with a pi of about 3. 14.

The general method of cutting circle is found in middle school mathematics textbooks. However, it must be noted that it is largely just a method to calculate pi, which is C.

=π*d seems to be a fact, and this method only determines 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.