Pentagon: A 5 Sided Shape

Introduction

A pentagon is a five-sided polygon, meaning it has five straight lines or edges that enclose its area. While the shape is considered a regular polygon, meaning all its sides and angles are equal, it has the unique distinction of being the only five-sided polygon. Drawing a pentagon is easy, but understanding a bit of its geometric structure helps in understanding why it has the shape and form it has.

History of Pentagon

The first documented use of the pentagon was an ancient Greek term that was used to describe a five-sided polygon. In the days of Euclidean geometry, it was a fundamental shape and was used as a symbol for the fifth element in the theory of four elements. Later, in the 15th century, the shape was used for constructing fortresses with five bastions. By the 19th century, the shape achieved its name and its usage began to be generalized in various applications.

Structure of Pentagon

A pentagon is composed of four triangles. Each triangle has three sides and three angles, with two sides and two of the three angles being shared with other triangles. Adding up the number of sides and angles of each triangle, the total number of sides is five and the total number of angles is fifteen.

The interior angles of a pentagon are all equal and can be calculated by taking the second angle of a triangle, subtracting it by the first angle, then subtracting that amount from 180 degrees. For example, if the first angle of a triangle is 30 degrees, the second is 60 degrees and the total angle is 180 degrees, the internal angle of the pentagon is 90 degrees.

Conclusion

The pentagon is a very special and unique shape. Its five sides and 15 angles define its structure and provide a great example of why shapes are so important in mathematics. Understanding this shape helps in understanding the principles of geometry such as angles, shapes, and other related concepts.