Polygon |
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A polygon is a closed figure made up of 3 or more line segments. |

Figure 1. |
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Above are a few examples of figures that are polygons.

A figure is not a polygon if:

It is an open figure.

Figure 2. |
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The sides of the figure overlap.

Figure 3. |
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It has a side that is not a line segment.

Figure 4. |
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Polygons can be named by the number of sides they have. Here are some examples:

Figure 5. |
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Interior Angles |
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The interior angles of a polygon sum to (n – 2)180 degrees, where n is the number of sides. |

Figure 6. |
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The above figure has 6 sides, so:

(6 - 2)180 = (4)180 = 720

It has 720 degrees.

Exterior Angles |
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For any polygon, all exterior angles sum to 360 degrees. |

Figure 7. |
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All of the green angles of this polygon sum to 360 degrees.

Regular Polygons |
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A regular polygon is a polygon where every side is equal to one another, and every angle is equal to one another. |

Below are two examples of regular polygons:

Figure 8. |
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