polygon

Polygons are manysided plane figures, the sides
and angles of which may be equal or unequal, giving symmetrical or
asymmetrical shapes. The simplest figure is the equilateral triangle
(A1) which has all sides and angles equal. The isosceles triangle
(A2) has two sides equal while (A3), which happens to be obtuse, has
sides of differing length. The simplest quadrilateral (B1) is the
square with equal sides and equal internal angles. The rectangle (B2)
has two pairs of equal and opposite sides with equal internal angles.
The parallelogram (B3) has two pairs of equal and opposite parallel
sides. The trapezium (B4) has only two parallel sides. The regular
pentagon (C) has five equal sides and the regular hexagon (D), six.


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, nonintersecting
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 
10^{6} 
179.99964° 
regular googolgon 
10^{100} 
180° (approx.) 
Related category
• POLYGONS
