Octagon

Shown above is a regular octagon. An octagon is a polygon with eight sides an eight internal angles. This polygon can be seen in such signs as stop signs as shown below.

Stop sign

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 octagon 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 = 8 Q2. = 8 Q3. = 8 Q4. = 45 Q5. = 135

Characteristics of a regular octagon:

Characteristics Number of sides = 8 Number of vertices = 8 Interior angle = 135 Exterior angle = 45 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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