Divide the circle into several parts evenly and you can make an approximate rectangle. The width of the rectangle is equal to the radius (r) of the circle, and the length of the rectangle is half the circumference (c) of the circle. The area of a rectangle is a×b, and the area of a circle is: the radius (r) of the circle times the half circumference c, and S=r×(C/2)=r×(2r×π/2)=r2×π.

The area of a circle refers to the size of the plane space occupied by the circle, which is often expressed by S. The circle is a regular plane geometry figure, and there are many calculation methods, such as Kepler method and cavalli method.

Regional origin of circle:

Kepler,/kloc-a German astronomer in the 6th century, worked as a math teacher. He is very interested in finding this area and has conducted in-depth research. He thought that ancient mathematicians used division to find the area of a circle, and the results were approximate. In order to improve the approximation, they constantly increase the number of segmentation.

But no matter how many times, tens of thousands of times, as long as it is limited, the approximate value of the circular area will always be obtained. In order to get the accurate value of the circle area, it is necessary to divide the circle into an infinite number of equal parts.

Kepler also imitated the method of cutting watermelon and divided the circle into many small sectors; The difference is that he divided the circle into infinitely many small sectors from the beginning. The area of a circle is equal to the sum of the areas of an infinite number of small sectors, so in the last formula, the sum of the areas of small arcs is the circumference of the circle 2πR, so there is S=r2×π. This is the familiar formula of circular area.