polygon

The polygon ABCD is an irregular quadrilateral with acute angles at A, C, and D and a reentrant angle at B. AC and BD are its diagonals.

A plane closed figure whose sides are straight lines. The term polygon (from the Greek poly for "many" and gwnos for "angle") sometimes also refers to the interior of the polygon (the open area that this path encloses) or to the union of both.

A polygon is simple if it is described by a single, non-intersecting boundary; otherwise it is said to be complex. A simple polygon is called convex if it has no internal angles greater than 180° otherwise it is called concave. A polygon is called regular if all its sides are of equal length and all its angles are equal. Any polygon, regular or irregular, has as many angles as it has sides.

Regular polygons
name	sides	interior angle = 180° - (360°/sides)
equilateral triangle	3	60°
square	4	90°
regular pentagon	5	108°
regular hexagon	6	120°
regular heptagon	7	128.57° (approx.)
regular octagon	8	135°
regular nonagon	9	140°
regular decagon	10	144°
regular hectagon	100	176.4°
regular megagon	10⁶	179.99964°
regular googolgon	10¹⁰⁰	180° (approx.)

Related category

• POLYGONS

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