# 2D shapes – Decagon

A decagon is a polygon that consists of ten sides and ten angles. The word “decagon” is derived from the Latin words “deca,” meaning ten, and “gonia,” meaning angle. It is classified as a regular polygon because all of its sides have equal lengths and all of its angles have equal measures.

Properties of a Decagon:

1. Sides: A decagon has ten sides, which means it has ten line segments connecting its ten vertices (corner points).
2. Angles: Each interior angle of a decagon measures 144 degrees, and each exterior angle measures 36 degrees. The sum of all the interior angles of a decagon is 1440 degrees.
3. Symmetry: A decagon exhibits rotational symmetry of order 10, which means it can be rotated by multiples of 36 degrees to coincide with its original position.
4. Diagonals: A decagon has 35 diagonals, which are line segments connecting any two non-adjacent vertices.
5. Area: To calculate the area of a regular decagon, you can divide it into ten congruent isosceles triangles.

In practical terms, a decagon can be observed in various contexts. For example, a stop sign typically has the shape of a regular octagon with a smaller octagonal region in the middle, creating a decagon-like appearance.

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