Dodecagon: Sides, Area & Angles

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  • 0:02 Dodecagons and Polygons
  • 0:43 Sides and Angles
  • 2:08 Area of Dodecagon
  • 2:38 Dodecagons Examples
  • 3:50 Lesson Summary
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Lesson Transcript
Instructor: Vanessa Botts
A dodecagon is a polygon with twelve sides and twelve angles. In this lesson, you will learn about this polygon - its sides, angles, and how to compute the area. A quiz will follow the lesson.

Dodecagons and Polygons

The term dodecagon is derived from the Greek language, where dodeca means twelve and gono stands for angle. This means a dodecagon has twelve angles and as such also has twelve sides.

This figure is a polygon which, incidentally, is also word that comes from this ancient language and means 'figure with many angles.' Didn't you know you could learn a second language while also learning math? Pretty cool!

A dodecagon looks like this:

dodecagon figure

You may find it interesting to know that quite a few coins from several different countries such as England, Australia, Croatia, and Canada have had this shape in the past.

Sides and Angles of Dodecagon

To be considered a regular dodecagon, each side has to have the same length, and therefore, each angle will have the same measurement, which happens to be 150 degrees. This would make the sum of its interior angles equal to 1800 degrees. Okay, 1800 is a pretty big number, especially considering that the interior angles of a square add up to a measly 360 degrees!

We can also figure out the sum of the interior angles with the method that is used for calculating the sum of interior angles for any polygon: (n - 2) * 180. The calculations are based on how many sides (or n) the polygon has. To compute the sum of the interior angles, all you need to do is subtract 2 from the number of angles in the polygon and then multiply that number times 180.

Let's try the actual calculation for a regular dodecagon:

Step 1: 12 - 2 = 10 (subtract 2 from the number of sides of the dodecagon)

Step 2: 10 * 180 = 1800 (multiply your result from the first step by 180)

See? We have just proven that the sum of the interior angles of a dodecagon is, in fact, 1800 degrees. Now, we will go further by venturing into computing the area for this interesting figure.

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