出典:Wikipedia
出典:『Wikipedia』 (2011/05/29 04:10 UTC 版)
In geometry, a heptagon (or septagon) is a polygon with seven sides and seven angles. In a regular heptagon, in which all sides and all angles are equal, the sides meet at an angle of 5π/7 radians, 128.5714286 degrees. Its Schläfli symbol is {7}. The area (A) of a regular heptagon of side length a is given by