It has been three and a half millennia 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 in such a way that no matter what these values are, the result is 3, 14.
This is the necessary information for the formula for the perimeter of a circle.
Native to Ancient Egypt
This number (rounded 3, 1415926535) has been used in problem solving ever since, denoted by the letter "π" (pronounced "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 18th century. And since then, the formula for the perimeter of a circle contains "π".
What is the glass and thread here for?
There is a simple and interesting experiment, during which the formula for the perimeter of a circle (that is, the circumference of a circle) is obtained.
What you need for it:
- ordinary glass (can be replaced with any object with a round bottom);
- thread;
- ruler.
Experiment progress:
- Wrap the thread around the glass once.
- Unwinding the thread.
- Measuring its length with a ruler.
- Measure the diameter of the bottom of the glass (or any other object taken for the experiment).
- Calculate the ratio of the first value to the second.
This is how the number "π" is obtained. And with whatever round objects the experiment is carried out, it will always be constant and equal to 3, 14.
Circle perimeter formula
Formula is a diminutive of forma. Not only mathematics, but also physics and other exact sciences use concise 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 equidistant from the given point (it is the center of the circle).
The circumference of a circle is denoted by the letter C, and its diameter by the letter d. The first formula looks like this:
C=πd.
Radius is denoted by the letter r. The formula for the perimeter of a circle containing it is:
C=2πr.
This method calculates the length of all circles.
