## Prisms

Prisms are solids (three‐dimensional figures) that, unlike planar figures, occupy space. They come in many shapes and sizes. Every prism has the following characteristics:

• Bases: A prism has two bases, which are congruent polygons lying in parallel planes.
• Lateral edges: The lines formed by connecting the corresponding vertices, which form a sequence of parallel segments.
• Lateral faces: The parallelograms formed by the lateral edges.

A prism is named by the polygon that forms its base, as follows:

• Altitude: A segment perpendicular to the planes of the bases with an endpoint in each plane.
• Oblique prism: A prism whose lateral edges are not perpendicular to the base.
• Right prism: A prism whose lateral edges are perpendicular to the bases. In a right prism, a lateral edge is also an altitude.

In Figure 1, prism (a) is a right triangular prism, prism (b) is a right rectangular prism, and prism (c) is an oblique pentagonal prism. The altitude in prism (c) is called h.