An 11-sided polygon is called a hendecagon. In order for an 11-sided shape to be considered a hendecagon, its sides must all be straight and form a closed shape.
Know MoreThe name for a hendecagon is derived from "hendeka," which is the Greek word for 11. Like other polygons, hendecagons can be either regular or irregular. A regular hendecagon consists of 11 sides equal in length and internal angles of approximately 147.273 degrees. An irregular hendecagon is any 11-sided polygon where one or more of the sides are different lengths from the others. An example of a real life hendacagon is the Canadian loonie.
Learn more in ShapesA 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.
Full Answer >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.
Full Answer >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.
Full Answer >A nine-sided polygon is commonly called a nonagon. This polygon, which has nine edges, or vertices, is also called an enneagon. The term enneagon is preferable, but less popular than the name nonagon because the latter is simpler to spell and pronounce, according to Wolfram MathWorld.
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