Circle perimeter formula: history, experiment

Three and a half millennia have passed since the ancient Egyptians discovered a very important fact for mathematics. Namely: the length that the circle has is related to the diameter of this figure so that no matter what the given values ​​are, the result is 3.14.

This is the necessary information for the circle perimeter formula.

Originally from ancient Egypt

This number (rounded 3, 1415926535) has been used since then in solving problems, denoting it with the letter “π” (read “pi”).

It is named after the initial letter of the Greek word "periphery", which is, in fact, a circle.

This designation was introduced later, in the XVIII century. And since then, the circle perimeter formula contains “π”.

What is glass and thread here for?

There is a simple and interesting experiment in which the formula for the perimeter of a circle (that is, the circumference) is obtained.

What will be required for him:

• ordinary glass (can be replaced with any object with a round bottom);
• thread;
• ruler.

The progress of the experiment:

1. Wrap a glass with a thread once.
2. Expand the thread.
3. We measure its length with a ruler.
4. We measure the diameter of the bottom of the glass (or any other object taken for the experiment).
5. We calculate the ratio of the first quantity to the second.

And so the number π is obtained. And no matter what round objects the experiment is conducted with, it will always be constant and equal to 3.14.

Circle perimeter formula

The word "formula" is a diminutive of forma. Not only mathematics, but also physics and other exact sciences uses concise statements of statements containing various quantities and logical conclusions.

A circle is a closed flat curved line. It should consist of all those points on the plane that are equally remote from the given point (it is the center of the circle).

The circumference of the circle is denoted by the letter C, and its diameter by the letter d. The first formula looks like this:

C = πd.

The radius is indicated by the letter r. The circle perimeter formula containing it is as follows:

C = 2πr.

In this way, the length of all circles is calculated.