B is an ear because the line between C and D is completely inside the shape
. C is a mouth because the line between A and B is completely outside the shape.
A vertex is a corner. It is a point where two or more lines, curves, rays, or sides meet, and is often represented by letters such as , , and .
For example, the vertex of an angle is the point where the two edges of the angle intersect, and a vertex of a cube is simply one of its corners—of which there are 8.
The concept of vertex applies to both two-dimensional and three-dimensional geometrical objects. For example, a tetrahedron has 4 vertices, and a pentagon has 5 vertices.
- ↑ "Compendium of Mathematical Symbols". Math Vault. 2020-03-01. Retrieved 2020-08-16.
- ↑ "What Are Vertices in Math?". Sciencing. Retrieved 2020-08-16.
- ↑ "Vertices, Edges and Faces". www.mathsisfun.com. Retrieved 2020-08-16.