Sec 1-6
Concept: Polygons
Objective: Given a figure, we will
identify and name it if it is a polygon as
measured by a scoring guide
Vocabulary:
Polygon: a plane figure that meets these 2 criteria
1. It is formed by three or more line segments
called sides
2. each side intersects exactly two sides, one
at each endpoint, so that no two sides with a common
endpoint are collinear.
Vertex
N
O
S
W
Polygon SNOW
Example 1: Determine which shapes are polygons.
If a shape is a polygon, then state if it is concave or
convex.
A
B
C
A - yes
D
concave
B - no
C - yes
concave
D - yes
convex
Names of Polygons: Handout
You have 10 min. to do this handout,
then we will go over it
Regular Polygon:
A regular polygon is both
equilateral and equiangular
Example 2: Each figure is a regular polygon.
Expressions are given for two sides lengths.
Find the value of x.
x2+5x+13
7x+34
11x-14
x2+10x-7
7x+34 = 11x-14
x2+5x+13 = x2+10x-7
48=4x
20=5x
12=x
4=x
Example 3: The expressions (3x+63)° and (7x-45)°
represent the measures of two angles of a regular
decagon. Find the measure of an angle of the
decagon.
3x+63=7x-45
3(27)+63
108=4x
=144°
27=x
Example 4: Draw a figure that fits
the description.
1.
A quadrilateral that is not regular
2.
A concave pentagon
Example 5 # 31 p. 46
Example 6 # 33 & 36 p. 46
Today’s Work: