Download A polygon is a closed figure

Lesson 3-4
Polygons
A polygon is a closed figure
No, not a polygon
Yes, a polygon
A polygon formed by a finite number of
coplanar segments
No, not a polygon
Yes, a polygon
A polygon has segments that intersect exactly two
other sides, but only at their endpoints.
No, not a polygon
Yes, a polygon
Definition of a Polygon
A closed figure formed by a finite
number of coplanar segments such
that the segments intersects
exactly two other sides, but only
at their endpoints.
Classifications of a Polygon
Convex
Concave
Regular
Irregular
Convex Polygon
No line containing a side of the polygon
contains a point in its interior
Concave Polygon
the opposite of convex
(think the opening of a cave)
Regular Polygon
A convex polygon in which all angles have the same
measure and all sides are the same length
Irregular Polygon
Two sides (or two interior angles) are not congruent
Polygon Names
3 sides
Triangle
4 sides
Quadrilateral
5 sides
Pentagon
6 sides
Hexagon
7 sides
Heptagon
8 sides
Octagon
9 sides
Nonagon
10 sides
Decagon
12 sides
n sides
Dodecagon
n-gon
Diagonals of a Polygon
a segment connecting nonconsecutive
vertices of a polygon
For a convex polygon with n sides:
The sum of the interior angles is
n  2 180
The measure of one interior angle is
n  2 180
n
The sum of the exterior angles is
360
The measure of one exterior angle is
360
n