It depends on how it unfolds. If it is unfolded like the side of a cylinder, it should be zigzag, but in practice, it is meaningless to know the unfolded diagram. For the surface area of a sphere, we basically adopt the method of integration, and the area S = 4 π r 2 can be obtained by integrating the volume.

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. The orthographic projection of a sphere on any plane is a circle with the same size, and the diameter of the projected circle is equal to the diameter of the sphere.

Extended data:

Cut a ball with a plane, the cross section is round. The cross section of a ball has the following properties: the line connecting the center of the ball with the center of the cross section is perpendicular to the cross section. The distance d from the center of the sphere to the cross section has the following relations with the radius r of the center of the sphere and the radius r of the cross section: r 2 = r 2-d 2.

A circle whose sphere is cut by a plane passing through the center of the sphere is called a big 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.

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