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Shown above is a regular hexagon. A
regular hexagon has six sides of equal length, each couple intersecting to form a vertex
of which there are six. This polygon has six internal angles of equal measure and
has six external angles of equal measure.
Exterior and Interior angles

Characteristics of a
regular hexagon:
 | Number of sides = 6:
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 | Number of vertices =
6:
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 | Interior angle =
120°:
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 | Exterior angle = 60°:
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 | Exterior angle
multiplied by the number of sides = 360°. (60° X 6 = 360°):
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 | Number of sides =
number of vertices:
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Now ask yourself how might you find the the internal angle and
the external angle of this regular hexagon and every other regular polygon of which there
are an infinite number.
Take the first three regular polygons that have been
encountered so far, the external angle of the equilateral triangle is 120°, multiply this
by the number of sides or vertices on the triangle and the calculation should read as
follows -- 120° x 3 = 360°.
Likewise with the square, its external angle is 90° and it has
four sides, thus leading to a calculation again of the external angle of the square
multiplied by the number of sides on the square -- 90° x 4
= 360°.
Taking into consideration the regular pentagon, it has five
sides and an external angle of 72° and when multiplied, one by the other
-- 72° x 5 = 360°.
What can be concluded from this is that when the exterior angle
of a regular polygon is multiplied by the number of sides of the polygon the answer will
always be 360°.
Letting Ea = Exterior angle and n = number of sides or
vertices, for any regular polygon, Ea x n = 360° hence, Ea = 360°/n .
- So for the regular hexagon shown above n = 6, thus leading to an external angle of
Ea, when Ea = 360°/n then Ea = 360°/6 and Ea = 60°.
If the exterior angle + the interior angle equal 180°,
Then 180°- the exterior angle = the interior angle,
Therefore the interior angle must be = 120°.

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Table of Contents
What is a Polyhedron?
Polygons
Regular
Irregular
Platonic-Solids
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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