Common geometric bodies are spheres, circles, cubes, triangular cones (polygonal cones), cylinders, cones, rings, frustums, cuboids and so on. The concept of geometry comes from people's mathematical abstraction of various objects in the objective world. When people only consider the mathematical properties of an object, such as its shape, size and positional relationship, but not its physical, chemical, biological and social properties, they get the concept of geometric body.
The surface surrounding the geometry is called the interface or surface of the geometry, the intersection line of different interfaces is called the edge line of the geometry, and the intersection point of different edge lines is called the vertex of the geometry.
Geometry can also be regarded as a limited space area divided by several geometric surfaces in space. Solid geometry first studies the geometric properties of some relatively simple geometric figures, such as polyhedron, rotator and their combinations. In geometry, a finite body surrounded by several geometric surfaces (planes or surfaces) is called geometry, the surfaces around geometry are called geometric interfaces or surfaces, the intersection lines of different interfaces are called geometric edge lines, and the intersection points of different edge lines are called geometric vertices. Geometry can also be regarded as the division of several geometric surfaces in space.
Basic geometric classification
The body is surrounded by the face. Surfaces have planes and surfaces. For example, a cuboid is surrounded by six planes; The ball is surrounded by a curved surface; A cylinder is surrounded by a curved surface and two planes. According to the characteristics of the surface, the main element of the body, the body can be divided into two categories:
The first kind is surface geometry, also called surface body. A surface entity is a geometric figure surrounded by a surface or a surface and a plane, and the projection of a surface entity is the combination of the projections of the surface and the plane that make up the surface entity. Common solid surfaces are rotating bodies, such as cylinders, cones, spheres and rings.
The second is plane geometry surrounded by planes, and the geometry surrounded by several plane polygons is called polyhedron. The polygon surrounding a polyhedron is called the face of the polyhedron. The common edge of two faces is called the edge of a polyhedron. A polyhedron has at least four faces. Such as prisms and cubes.