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An 8-sided polygon is called an octagon. One common use of the octagon is in the iconic red stop sign that's used throughout the United States.

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A polygon with 25 sides is called a icosikaipentagon. Polygon names are constructed according to the tens unit and the single digit unit.

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An 11-sided polygon is called a hendecagon. It is also known as the undecagon or unidecagon. However, the term "hendecagon" takes precedence over these variants because of its consistency in using a Greek prefix and suffix, instead of combining a Roman prefix with a Greek suffix.

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A four-sided polygon is known as a quadrilateral. There are various types of quadrilaterals, but the most recognized are the square, rectangle, rhombus, trapezoid and the parallelogram. Quadrilaterals are always flat shapes that have four straight edges and four corners or vertices.

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A 12-sided two-dimensional polygon is called a dodecagon. A regular dodecagon has 12 sides that are all the exact same length and internal angles that are 150 degrees each. Since there are 12 internal angles, the total internal angles add up to 1,800 degrees.

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A 20-sided polygon is called an icosagon. Along with having 20 sides, all icosagons have 20 interior angles that add up to a total of 3240 degrees.

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The name of a 10-sided polygon is a decagon. The term "decagon" comes from the modern Latin word "decagonum" and from the Greek "dekagonon," which is a combination of "deka," meaning "ten" and "gonia," meaning "corner" or "angle."

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The accepted name of a 12-sided polygon is "dodecagon." A polygon is a two-dimensional shape consisting of angles and straight lines in a closed system. The word "polygon" comes from the Greek "poly," which means "many" and "gon," which means "sides."

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A polygon can be any number of shapes. A polygon is a two dimensional shape made of at least 3 straight lines that do not cross and is a closed shape. Examples of polygons would include triangles, squares, rectangles, hexagons, and octagons.

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The degrees of a polygon, or the sum of its angles, depends on the number of sides the polygon has. The sum of the degrees of the angles of a polygon equals 180(n-2), where n equals the number of sides of the polygon.