Naming Polygons: Polygons have names based on the number of

Naming Polygons: Polygons have names based on the number of

7.3-Formulas Involving Polygons
Naming Polygons:
Polygons have names based on the number of sides that they have. Here is a
chart for naming them.
# of sides(or
vertices)
3
4
5
6
7
8
Polygon
Triangle
Quadrilateral
Pentagon
Hexagon
Heptagon
Octagon
# of sides(or
vertices)
9
10
12
15
n
Polygon
Nonagon
Decagon
Dodecagon
Pentadecagon
n-gon
You should know these names.
What is the sum of the measures of the 5 angles in the figure?
Chapter 7 Page 1
Theorem: The sum of the measures of the angles of a polygon with n sides is
given by the formula Si = (n - 2)·180°
Theorem: If one exterior angle is taken at each vertex, the sum of the
measures of the exterior angles of a polygon is always 360°
Theorem: The number of diagonals that can be drawn in a polygon of n sides
is given by the formula
d
n(n  3)
2
Ex 1
Find the sum of the measures of the angles of a 22-gon.
Ex 2
How many diagonals does a decagon have?
Chapter 7 Page 2
Ex 3
Find the sum of the exterior angles(one per vertex) of an octagon.
Ex 4
Name the polygon with 252 diagonals.
Ex 5
Name the polygon whose interior angles sum to 1260.
Ex 6
Chapter 7 Page 3
Find the value of x
Chapter 7 Page 4