Presented here is a regular nine sided figure called a regular nonagon. this figure can be clearly distinguished from the irregular nonagon shown below. The regular nonagon can be seen to have equal sides and equal vertices.

Irregular nonagon

Interior and exterior angles

Tutorial

Questions to answer:              

Letting n = number of sides, Ea = external angle and Ia = internal angle.

1. How many sides has the regular nonagon shown above?    

2. How many internal angles has it?   

3. How many vertices has it?   

4. What is the measure of its external angle?  

5. What is the measure of its internal angle?  

Answers Q1 = 9 Q2. = 9 Q3. = 9 Q4. = 40 Q5. = 140

Characteristics of a regular nonagon:

Characteristics Number of sides = 9 Number of vertices = 9 Interior angle = 140 Exterior angle = 40 Exterior angle X No. of sides = 360

Table of Contents        

What is a Polyhedron?

Polygons

     Regular

     Irregular

Platonic-Solids

Tetrahedron

Octahedron         Hexahedron

Icosahedron         Dodecahedron

Relationships

Archimedean- Solids

Truncated Tetrahedron

Truncated Octahedron

Truncated Hexahedron

Truncated Icosahedron

Truncated Dodecahedron

Quasi-regular Polyhedra

Rhombi Archimedeans

Truncated Quasi-regulars

Snub Polyhedra

Polyhedra & Spherical Geometry

Prerequisite Knowledge

Spherical Projection of the Cube

Glossary of Terms

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