A prism is a polyhedron whose surface is formed by two equal and parallel faces called bases and by lateral faces that are called parallelograms. All the sections of the prism parallel to the bases are equal. Different types of prism are provided below.
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Prism Elements
In a prism the following elements can be distinguished :
- Bases ( B ): Each prism has two bases, both of which are equal and parallel.
- Faces ( C ): the parallelograms of the sides and bases.
- Height ( h ): distance between the two bases of the prism. In the case of the right prism, the length of the height h and that of the edges of the lateral faces coincide.
- Vertices ( V ): points where the faces of the prism meet.
- Diagonals (D) : segments that join two vertices that belong to different faces.
Types of Prism
The prisms can be classified according to four criteria :
Number of sides of the base
Types of prism on the bases of the number of sides that have their basis :
- Triangular prism: the bases are triangles (3 sides).
- Quadrangular prism: the bases are quadrilateral (4 sides).
- Pentagonal prism: the bases are pentagons (5 sides).
- Hexagonal prism: the bases are hexagons (6 sides).
Regular or irregular
- Regular prism: a prism is regular if its bases are regular polygons.
- Irregular Prism: Prisms are irregular if they have irregular polygons at their base.
Straight or oblique
- Right prism: if the axes of the polygons of the bases are perpendicular to the bases. The side faces are squares or rectangles.
- Oblique prism: it is one whose axes of the polygons of the bases are joined by an oblique line to the bases themselves.
Convex or concave
- Convex prism: the prism is convex if its bases are convex polygons.
- Concave prism: the concave prism has two equal concave polygons as bases.
See Also: Prisms Vs Pyramid
