A dodecagon is a polygon with twelve sides and twelve angles. Dodecagon may be a convex or a concave polygon.
The above figure is a dodecagon with twelve vertices named from A through L. In the above dodecagon, the sides are of varying length. It is to be noted that the sides need not be of the same length.

## Regular Dodecagon

A Regular Dodecagon is a dodecagon in which all twelve sides are of equal lengths. As all the sides are of equal length, all the angles will be equal.
Each interior angle is equal to 150o. Sum of interior angles = 1800o.

The above polygon is a regular decagon with each side is of 2 unit length.

We can construct a dodecagon by following the steps given hereunder:
Step 1: Draw a straight line and take a point O on it. Draw a circle with center O. Let A and B be the points where the line intersects the circle. Then, AB is the diameter and hence OA=OB=r, the radius of the circle.

Step 2: Draw an arc of radius equal to the diameter 2r with centers at A and B. Let the intersecting points of the arcs be X and Y.

Step 3: Join X and Y with a straight edge. The line segment $\overline{XY}$ will be perpendicular to the line segment $\overline{AB}$. Suppose that the line segment $\overline{XY}$ intersects the circle at the points C and D.

Step 4: Draw arcs with radius equal to r with centers A, B, C, and D. Let the intersecting points of the arcs with the circle be V1, V2, V3, V4, V5, V6, V7 and V8. Join each point (including A, B, C, D) with its adjacent point using a straight edge.

By removing the arcs and circumscribed circle, we get a dodecagon.

### Area of a Polygon

 Dodecagon Area A Polygon A Concave Polygon is A Convex Polygon A Regular Polygon All Types of Polygons Area of any Polygon Congruent Polygon Frequency Polygon Pentagon Polygons Similar Polygon What is a Irregular Polygon
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