What is a shape called with 11 sides?

The shape with 11 sides is called an undecagon or hendecagon.

Here are some key features and properties of an undecagon:

1. Number of Sides: An undecagon has 11 sides, which is why the name "undecagon" is derived from the Latin word "undecim," meaning eleven.

2. Number of Vertices: An undecagon also has 11 vertices. These are the points where the sides of the shape intersect.

3. Interior Angles: The sum of the interior angles in any undecagon is equal to (11 - 2) × 180 degrees, which is 1620 degrees. Each interior angle in a regular undecagon measures approximately 147.3 degrees.

4. Exterior Angles: The sum of the exterior angles in any undecagon is always 360 degrees. Each exterior angle in a regular undecagon measures approximately 32.7 degrees.

5. Regular and Irregular: An undecagon can be regular or irregular. A regular undecagon has sides of equal length and angles of equal measure, while an irregular undecagon has sides and angles that vary in measurements.

6. Regular Undecagon: In a regular undecagon, all sides and angles are congruent. Additionally, the interior and exterior angles at each vertex are also congruent.

7. Construction: Constructing a regular undecagon using a compass and straightedge is possible but somewhat complex. Various geometric methods exist to obtain an accurate approximation of a regular undecagon.

These are some general details about an undecagon. However, it is important to note that this shape is less commonly encountered in everyday life compared to shapes with fewer sides, like triangles, rectangles, or pentagons.