First of all, a plane figure is composed of points, lines and surfaces, and the relationship between them is linear, that is, there is only one straight line between points, and there is only an intersecting or parallel relationship between lines. Common plane figures are triangle, quadrilateral, circle and so on. The three-dimensional model is composed of multiple surfaces, which can be planes or surfaces. The relationship between them is nonlinear, that is, the surfaces can intersect, tangent or separate. Common three-dimensional models are cubes, cylinders and cones.
Secondly, the properties of plane graphics can be described by Euclidean geometry axioms, such as parallel axioms and vertical axioms. The properties of three-dimensional models need to be described by concepts such as volume and surface area. For example, the volume of a cube is equal to the cube with its side length, and the surface area is equal to the sum of the areas of six faces.
In addition, there are differences between plane graphics and three-dimensional models in solving problems. For plane graphics problems, we usually need to use geometric theorems and properties for reasoning and proof; For three-dimensional model problems, it is necessary to use spatial imagination and solid geometry knowledge to analyze and calculate.
In a word, although plane graphics and three-dimensional models belong to the category of geometry, they are obviously different in terms of expression, property description and problem-solving methods. Mastering these two concepts is very important for junior high school students, because they not only help to cultivate our logical thinking ability, but also lay a solid foundation for us to learn more advanced mathematics knowledge in senior high school.