Calculation formula of sphere area: sphere area = 4 π r 2, and r is sphere radius. Where π is pi (approximately equal to 3. 14 159) and r is the radius of the ball. First, determine the radius of the ball. If you know the diameter (d) of the ball, you can divide d by 2 to get the radius (r=d/2). Then, the radius value is substituted into the formula to calculate the surface area.

For example, suppose a ball has a radius of 5cm and a surface area of 4 π (5 cm) 2. Through calculation, the surface area is ≈3 14. 16 cm. Please note that the calculation result of surface area will be expressed in square units (such as square centimeters, square meters, etc.). ).

A space geometry, in which a semicircle rotates a Zhou Suocheng around a straight line equivalent to its diameter, is called a sphere, and the radius of the semicircle is the radius of the sphere. A sphere is a three-dimensional figure with only one continuous surface, which is called a sphere.

Definition of sphere

The space geometry of a semicircle rotating a Zhou Suocheng around a straight line with its diameter is called a sphere, and the figure shown in figure 1 is a sphere. Sphere is a three-dimensional figure with a continuous surface, and the geometry surrounded by sphere is called sphere. There is no absolute sphere in the world. Absolute spheres exist only in theory. But in a weightless environment (such as space), the droplets will automatically form an absolute sphere.

Spherical characteristics

1, the straight line connecting the center of the sphere and the center of the section is perpendicular to the section.

2. the distance d from the center of the sphere to the cross section has the following relationship with the radius r of the center of the sphere and the radius r of the cross section: r 2 = r 2-d 2.

3. A circle whose sphere is cut by a plane passing through the center of the sphere is called a great circle, and a circle cut by a section not passing through the center of the sphere is called a small circle. On the sphere, the length of the shortest connecting line between two points is the length of the bad arc between these two points through the great circle of these two points. We call this arc length the spherical distance between two points.