A polygon is a flat geometric figure that is delimited by different joined segments.
Each one is made up of sides or segments, the vertices or points of union of the sides and the angles, which are the spaces formed between two rays that meet at a point.
Regarding their classification, they are divided into regular and irregular (if all the sides and angles are equal, it is a regular polygon). Another way to classify them is by the number of sides they present. The octagon, enegon, and decagon are polygons that have eight, nine, and ten sides respectively.
Octagon
This geometric figure is regular when its sides and angles are congruent, that is, equal.
Its angles are all 135 degrees and in its interior it is possible to form eight triangles.
To calculate its perimeter, you can multiply the length of a side by eight. To calculate its area, the perimeter must be multiplied by the apothem divided by two (the apothem is the distance between the center of a polygon and the central point that is on each side of a figure).
Like other figures, it is possible to draw a perfect circumference through the inside or outside of its sides. If the sides of this polygon are not equal to each other, the octagon is irregular.
Eneagon or nonagon
As the name suggests, this geometric figure has nine sides and nine vertices.
If all its sides are the same length and its internal angles are equal, it is a regular figure. Each of its angles is 140 degrees.
If we multiply the length of each side by nine we get the perimeter. Obviously, the eneagon can be irregular.
Decagon
The Greek prefix deca indicates that this figure has ten equal sides.
This polygon also has ten vertices, ten angles, and thirty-five diagonals.
To calculate its area it is necessary to know the length of its sides or the length of its apothem.
Beyond math
The different geometric figures are basic "tools" of technical drawing and are used to plan an architectural construction or to design all kinds of objects of everyday life. Likewise, nature presents very unique geometric shapes, such as the hexagonal shape of the honeycombs of bees or some anatomical structures of the animal and plant kingdom.
Geometric patterns in nature are known as fractals. Knowledge of fractals is very useful in seismology, biology or in any form of terrestrial measurement. Knowledge of fractals has allowed us to better understand the order of nature.
Photo: Fotolia - ngaga35
