Undecagon

Elementary School

Definition

A polygon that has 11 sides. It is more commonly known as a hendecagon. Hendecagons that have 11 equal number of angles are regular hendecagons. It will have internal angles of 147.27 degrees each.

Worked examples

\(\)Number of sides\( = 11\)

An undecagon is defined by having exactly 11 sides and 11 vertices.

\(\)Each interior angle\( = \frac{(11-2) \times 180^\circ}{11} = 147.27^\circ\)

In a regular undecagon, all interior angles are equal and measure about 147.27 degrees.

Common mistakes

\(\)Sum of interior angles\( = 11 \times 180^\circ\) → \(\)Sum of interior angles\( = (11-2) \times 180^\circ = 1620^\circ\) Use the formula \((n-2) \times 180^\circ\), not \(n \times 180^\circ\).
All undecagons have equal sides and angles → Only regular undecagons have equal sides and angles Irregular undecagons have 11 sides of different lengths and/or different angles.
\(\)Each exterior angle\( = 147.27^\circ\) → \(\)Each exterior angle\( = \frac{360^\circ}{11} \approx 32.73^\circ\) Exterior angles sum to 360° in any polygon; divide by the number of sides for a regular polygon.

Where you'll use it next

You'll apply polygon angle formulas to undecagons and other n-gons when studying geometry, trigonometry, and coordinate geometry, and when analyzing tessellations and symmetry in higher math.

Found in 1 StudyPug lesson

Mastering Polygon Classification in Geometry

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Dive into the world of polygons! Learn to identify and classify shapes, understand their properties, and discover real-world applications. Enhance your geometry skills with our comprehensive guide.

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