Sum of angles of a triangle to zero. For a spherical triangle, the sum of the angles is greater than 180° and can be up to 540°. Specifically, the sum of the angles is where "f" is the fraction of the sphere's area which is enclosed by the triangle. Note that spherical geometry does not satisfy several of Euclid's axioms (including the parallel postulate.) Angles between adjacent sides of a triangle are referred to as "interior" angles in Euclidean and other geometries. "Exterior" angles can be also defined, and the Euclidean triangle postulate can be formulated as the exterior angle theorem. One can also consider the
The Pentagon project for the U.S. Army. The Pentagon is the world's largest office building, with about of space, of which are used as offices. Some 23,000 military and civilian employees, and another 3,000 non-defense support personnel, work in the Pentagon. It has five sides, five floors above ground, two basement levels, and five ring corridors per floor with a total of of corridors. The central five-acre (20,000 m) pentagonal plaza is nicknamed "ground zero" on the presumption that it would be a prime target in a nuclear war. On September 11, 2001, exactly 60 years after the building's construction began, American