What does the word “polygon” mean?
What is the smallest number of
sides a polygon can have?
What is the largest number of
sides a polygon can have?
Triangle
Octagon
Quadrilateral
Nonagon
Pentagon
Decagon
Hexagon
Dodecagon
Heptagon
Hendecagon
n-gon
Hip Bone’s connected to the…
Classifying Polygons
Polygons with 3 sides… Triangles
Polygons with 4 sides… Quadrilaterals
Polygons with 5 sides.. Pentagons
But wait we have more polygons
Polygons with 6 sides… Hexagons
Polygons with 7 sides… Heptagons
Polygons with 8 sides… Octagons
But still we have more polygons
Polygons with 9 sides… Nonagons
Polygons with 10 sides… Decagons
Polygons with 12 sides… Dodecagons
And now we have our polygons
Important Terms
A VERTEX is
the point of
intersection of
two sides
A
B
F
A segment whose
endpoints are two
nonconsecutive
vertices is called
a DIAGONAL.
CONSECUTIVE
VERTICES are two
endpoints of any side.
C
E
D
Sides that share a vertex are called
CONSECUTIVE SIDES.
Polygons are named by listing its
vertices consecutively.
A
B
C
F
E
D
More Important Terms
EQUILATERAL - All sides are congruent
EQUIANGULAR - All angles are congruent
REGULAR - All sides and angles are congruent
Three more important terms
Interior
Angles
Exterior
Angles
SUPPLEMENTARY
the SUM of an interior angle and it’s corresponding exterior angle = 180o
Polygons can be CONCAVE or CONVEX
CONCAVE
CONVEX
Classify each polygon as convex or concave.
It’s what’s inside that counts 
Finding and using the interior angle measures
of polygons
What is the sum of the measures of the
interior angles of a triangle?
180°
180°
180°
What is the sum of the measures of the
interior angles of any quadrilateral?
360°
# of
sides
# of
triangles
Sum of
measures of
interior angles
3
1
1(180) = 180
4
2
2(180) = 360
5
3
3(180) = 540
6
4
4(180) = 720
n-2
(n-2) 180
n
If a convex polygon has n sides,
then the sum of the measure of the
interior angles is
(n – 2)(180°)
If you know the sum of the angles of a
regular polygon, how can you find the
measure of one of the congruent angles?
Regular
Polygon
Interior
angle sum
Triangle
180o
Quadrilateral
360o
Pentagon
Hexagon
Heptagon
Octagon
Decagon
Dodecagon
n-gon
Measure of
one angle
If a regular convex polygon
has n sides, then the measure
of one of the interior angles is
(n  2)180
n