How to calculate the area of a circle Formula for calculating the area of a circle: S = π×r2 =3. 14 16×r2 Formula for calculating the circumference of a circle: L = 2×π×r (area of a circle, that is, radius multiplied by radius multiplied by 3. 14) Known area of a circle is diameter: diameter.
Zu Chongzhi, an ancient Chinese mathematician, started with the inscribed circle of a regular hexagon, multiplied the number of sides, and approximated the area of the circle with the area of the inscribed circle of a regular polygon.
Mathematicians in ancient Greece started with regular polygons inscribed in a circle and circumscribed at the same time, increasing the number of their sides and approaching the area of the circle from the inside out.
Mathematicians in ancient India cut a circle into many small petals similar to watermelons, and then butted these small petals into a rectangle, replacing the area of the circle with the area of the rectangle.
Kepler,/kloc-a German astronomer in the 6th century, 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, so there is S=πr? .
A circle is a geometric figure, which refers to the set of all points on a plane whose distance to a fixed point is constant. This given point is called the center of the circle. The distance as a fixed value is called the radius of a circle. When a line segment rotates once around one of its endpoints on a plane, the trajectory of its other endpoint is a circle. There are countless circles in diameter; A circle has countless axes of symmetry. The diameter of a circle is twice the radius, and the radius of a circle is half the diameter.
When drawing a circle with a compass, the point where the needle tip is located is called the center of the circle, which is generally represented by the letter O. The line segment connecting the center of the circle with any point on the circle is called the radius, which is generally represented by the letter R. The length of the radius is the distance between the two corners of the compass. The line segment passing through the center of the circle and with both ends on the circle is called the diameter, which is generally represented by the letter D.
A circle is a curved figure on a plane and an axisymmetric figure. Its axis of symmetry is the straight line where the diameter lies, and the circle has countless axes of symmetry.
The formula related to a circle is 1, and the area of a semicircle is s semicircle = (π r 2)/2. (r is the radius).
2. The area of the circular ring: s great circle -S small circle = π (r 2-r 2) (r is the radius of the great circle and r is the radius of the small circle).
3. Circumference: C=2πr or c = π d..(d is the diameter and r is the radius).
4. The circumference of a semicircle: d+(πd)/2 or d+π r (d is the diameter and r is the radius).
5. Sector arc length L= central angle (radian system) ×R= nπR/ 180(θ is central angle) (R is sector radius).
6. Sector area S=nπ R? /360=LR/2(L is the arc length of the sector)
7. Radius of cone bottom surface r=nR/360(r is the radius of bottom surface) (N is the central angle)