Material preparation: paper and pencil.

1. First draw a square and divide it into four parts. Draw the diagonal of a square, draw a line segment with a quarter of the length of a small square on the diagonal, and connect the parts with the same radius with an arc to draw the shape of a circle. This step can be omitted when you practice drawing comprehensively in the future.

2. Erase unnecessary auxiliary lines and gently draw a dividing line between light and dark. Starting near the dividing line between light and dark, arrange cables with light and heavy lines.

3. Continue to arrange cables in this way, sweep out bright and dark gray surfaces, and finally draw a projection after overall adjustment.

Precautions:

Sphere can't be unfolded in reality, so it can only be approximated infinitely by mathematical methods. The finer the division, the closer to the actual situation. However, our life can be unfolded in abstract mathematics, which requires a series of changes in mathematical formulas, but this unfolding is also infinite approximation, which means it is actually impossible.

range

A figure composed of all points, whose distance to a fixed point in space is equal to a fixed length, is called a sphere. Sphere is a three-dimensional figure with a continuous surface, and the geometry surrounded by sphere is called sphere. (The center of the sphere is equal to the sphere everywhere. )

1, and the semicircle takes its diameter as the rotation axis.

2. The surface formed by rotation is called a sphere.

The geometry surrounded by a sphere is called a sphere.

The center of the semicircle is called the center of the sphere.

5. The length of the line segment connecting the center of the sphere and any point on the sphere is called the radius of the sphere.

6. The length of the line segment connecting two points on the sphere and passing through the center of the sphere is called the diameter of the sphere.