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Revision as of 16:53, 27 December 2001 by AxelBoldt (talk | contribs) (Polyhedra are not polygons.)(diff) ← Previous revision | Latest revision (diff) | Newer revision → (diff)Generally, the word polygon is used to refer to a two dimensional construction that encloses a space using straight lines. Regular polygons have sides that are of equal length and have equal angles between each side. Concave polygons have at least one internal angle that is greater than 180°, whereas convex polygons have all internal angles less than 180°. A cyclic polygon has all of its vertexes lying on the same circle. A polygon can belong to several classifications simultaneously; a square is a regular, convex, cyclic polygon, for example.
'Poly-' is from the Greek word for 'many' and '-gon' is a Greek combining form meaning 'angle'.
Regular Polygons
| Name | Sides | Angle* |
|---|---|---|
| Triangle | 3 | 60° |
| Square | 4 | 90° |
| Pentagon | 5 | 108° |
| Hexagon | 6 | 120° |
| Septagon | 7 | 128.57° |
| Octagon | 8 | 135° |
| Nonagon | 9 | 140° |
| Decagon | 10 | 144° |
| Hectagon | 100 | 176.4° |
| Megagon | 10 | 180.° (approx.) |
| Googolgon | 10 | 180.° (approx.) |
* Angle= 180°-(360°/ Sides )
Any polygon, regular or irregular, has as many angles as it has sides, and the sum of its angles is equal to (180°)*(s-2), where s is the number of its sides.