Pentagon Pentagon In geometry, a pentagon (from the Greek πέντε "pente" and γωνία "gonia", meaning "five" and "angle") is any five-sided polygon or 5-gon. The sum of the internal angles in a simple pentagon is 540°. A pentagon may be simple or self-intersecting. A self-intersecting "regular pentagon" (or "star pentagon") is called a pentagram. A "regular pentagon" has Schläfli symbol {5} and interior angles are 108°. A "regular pentagon" has five lines of reflectional symmetry, and rotational symmetry of order 5 (through 72°, 144°, 216° and 288°). The diagonals of a convex regular pentagon are in the golden ratio to its
The Pentagon records storage facility at some time after the end of the current war. A minimal amount of steel was used as it was in short supply during World War II. Instead, the Pentagon was built as a reinforced concrete structure, using 680,000 tons of sand dredged from the Potomac River, and a lagoon was created beneath the Pentagon's river entrance. To minimize steel usage, concrete ramps were built rather than installing elevators. Indiana limestone was used for the building's façade. Architectural and structural design work for the Pentagon proceeded simultaneously with construction, with initial drawings provided in early October 1941,