The enneahedron is a type of polyhedron. It is characterized by being formed by nine faces. In this, all the faces are polygons, with eight sides or less.

In other words, an enneahedron is a three-dimensional figure that is made up of several polygons. These can be triangles, quadrilaterals, pentagons, hexagons, heptagons, or even one of the faces can be an octagon. This is the case of the octagonal pyramid, which we will detail later.

It is worth mentioning that the enneahedron can have different shapes. Thus, there are 2606 possible types of convex enneahedra. That is, enneahedrons in which any two points in the figure can be joined by a straight line that remains within the polyhedron.

Another point to keep in mind is that there is no regular enneahedron. That is, in which their faces are regular polygons, with sides and interior angles of the same measure, all equal to each other.

Types of enneahedron

Some types of enneahedron are the following:

  • Octagonal pyramid: It is a pyramid whose base is an octagon and whose lateral faces are triangles that meet at a single point.
  • Heptagonal prism: It is a prism whose bases are the heptagons and the lateral faces are quadrilateral.

Elements of an enneahedron

The elements of an enneahedron are as follows:

The elements of an enneahedron, guided by the figure below, are:

  • Faces: They are the sides of the enneahedron.
  • Edges: It is the union of two faces. For example, the segment of the heptagonal prism shown in this article.
  • Vertices: They are those points where the edges meet. For example, the point where the faces of the octagonal pyramid meet, illustrated above.
  • Dihedral angle: It is formed by the union of two faces.
  • Polyhedron angle: It is one that is constituted by the sides that coincide in a single vertex.

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