fivesided

Fivesided is an adjective used to describe objects, shapes, or figures that have five sides. In geometry the term is often replaced by pentagonal or pentagon, but fivesided can be understood in descriptive or design contexts and informal writing.

A five-sided polygon is a pentagon. For any simple pentagon, the sum of interior angles is (5−2)×180 = 540 degrees, and the sum of exterior angles is 360 degrees. A pentagon may be convex (all interior angles less than 180 degrees) or concave (one or more interior angles greater than 180 degrees). A regular pentagon has five equal sides and five equal interior angles, each measuring 108 degrees.

Diagonals and relationships: In a regular pentagon, the five diagonals form a pentagram. The ratio of a diagonal to a side is the golden ratio, φ ≈ 1.618. The area of a regular pentagon with side length s can be expressed as (1/4)√(5(5+2√5)) s^2, which is approximately 1.720477 s^2.

Tilings and applications: Regular pentagons do not tile the plane by themselves, but pentagonal tilings can be achieved with a combination of pentagons and other polygons. Pentagonal shapes are also common in architecture and decorative design, where five-sided motifs appear in floor plans, jewelry, and ornamental panels.

Other usage: In non-geometric contexts, fivesided may be used descriptively to indicate five-sided symmetry or form, but pentagonal is the standard geometric term.