Section 2.3
Types of Polygons
A polygon is a closed plane figure
whose sides are segments that intersect only at their endpoints.
Using the definition of a polygon can you
give a reason why the following figures are NOT Polygons
A polygon can be either concave or convex.
A polygon is classified as convex if all line segments drawn between
any two vertices lies completely in the interior of the polygon.
A polygon is classified as convex if all interior angles are less than 1800.
Any polygon that is not convex is concave.
Examples of concave polygons
Polygons can be classified by their number
of sides.
1. A triangle is a polygon with
three sides.
2. A quadrilateral is a polygon
with four sides
3. A pentagon is a polygon with
five sides
4. A hexagon is a polygon with
six sides
5. A heptagon is a polygon with
seven sides
6. An octagon is a polygon with
eight sides
7. A nonagon is a polygon with
nine sides
8. A decagon is a polygon with
ten sides
9. A n-gon
is a polygon with n sides.
You can describe a polygon by comparing the
length of its sides or the measure of its angles.
1. 
If all the sides of a
polygon are congruent, then it is an equilateral polygon.
2. If all the angles of a
polygon are congruent, then it is an equiangular polygon.
3. 
If a polygon is both
equilateral and equiangular, then it is referred to as a regular
polygon.
Parts of a Polygon
Two vertices of a polygon connected by a side are called consecutive
vertices.
Two angles of a polygon that share a side are called consecutive
angles.
Two sides that share a vertex are called consecutive sides.
A segment that connects nonconsecutive vertices is called a diagonal.
To name a polygon, start at any vertex and
write consecutive vertices in order.
The name of
our example polygon is ABCDEF or CDEFAB
A line of symmetry is a line that divides a
figure into two congruent parts.
