The formula for the area of a circle is: S=πr_. Where s represents the area of the circle; π is pi, which is an infinite cycle decimal. Generally, there is no special requirement to calculate π ≈ 3.14; R is the radius of the circle.

For example, if the radius of a circle is 2 cm, then the area of the circle is 3. 14 times the square of 2, and the area of the circle is 12.56 cm. 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 small arcs is the circumference of the circle, which is the familiar formula of pi.