2. 8-5 Classifying Polygons
Warm Up
1. How do you name a ray? Under the ray
symbol, name first the endpoint and then
any other point on the ray.
2. What is the measure of an obtuse angle?
between 90° and 180°
3. How do you name a line?
Under the line symbol, name any two
points on a line.
4. What is true of supplementary angles?
The sum of their measures is 180°.
Course 2
3. 8-5 Classifying Polygons
Problem of the Day
Draw a polygon with 10 congruent sides.
Make 5 of the angles acute angles and
the other 5 reflex angles (greater than
180°).
Possible answer:
Course 2
6. 8-5 Classifying Polygons
Triangles and rectangles are examples of
polygons. A polygon is a closed plane figure
formed by three or more line segments. Each
line segment forms a side of the polygon, and
meets, but does not cross, another line
segment at a common point. This common point
is a vertex of a polygon.
Side
The polygon at
left has six
sides and six
Vertex
vertices.
Remember!
Vertices is plural for vertex.
Course 2
7. 8-5 Classifying Polygons
Additional Example 1: Identifying Polygons
Determine whether each figure is a polygon. If
it is not, explain why not.
A.
The figure is a
polygon. It is a
closed figure with
4 line segments.
Course 2
B.
The figure is not a
polygon. It is not a
closed figure.
8. 8-5 Classifying Polygons
Additional Example 1: Identifying Polygons
Determine whether each figure is a polygon. If
it is not, explain why not.
C.
The figure is not a
polygon. The
figure is not
formed by line
segments.
Course 2
D.
The figure is not a
polygon. There are
line segments in
the figure that
intersect.
9. 8-5 Classifying Polygons
Check It Out: Example 1
Determine whether each figure is a polygon. If
it is not, explain why not.
A.
The figure is a
polygon. It is a
closed figure with
5 line segments.
Course 2
B.
The figure is not a
polygon. It is not a
closed figure.
10. 8-5 Classifying Polygons
Check It Out: Example 1
Determine whether each figure is a polygon. If
it is not, explain why not.
C.
The figure is not a
polygon. The
figure is not
formed by line
segments.
Course 2
D.
The figure is not a
polygon. There are
line segments in
the figure that
intersect.
11. 8-5 Classifying Polygons
Polygons are classified by the number of sides
and angles they have.
Triangle
3 sides
3 angles
Heptagon
7 sides
7 angles
Course 2
Quadrilateral
4 sides
4 angles
Octagon
8 sides
8 angles
Pentagon
5 sides
5 angles
Nonagon
9 sides
9 angles
Hexagon
6 sides
6 angles
Decagon
10 sides
10 angles
13. 8-5 Insert Lesson Title Here
Classifying Polygons
Check It Out: Example 2
Name each polygon.
B.
A.
Quadrilateral
Course 2
Pentagon
14. 8-5 Insert Lesson Title Here
Classifying Polygons
A regular polygon is a polygon in
which all sides are congruent and all
angles are congruent.
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15. 8-5 Classifying Polygons
Additional Example 3: Identifying and Classifying
Regular Polygons
Name each polygon and tell whether it is a
regular polygon. If it is not, explain why not.
A.
The figure is a regular
quadrilateral. A regular
quadrilateral is also
called a square.
Course 2
B.
The figure is a
quadrilateral. It is not a
regular polygon because
all of the sides are not
congruent.
16. 8-5 Insert Lesson Title Here
Classifying Polygons
Check It Out: Example 3
Name each polygon and tell whether it is a
regular polygon. If it is not, explain why not.
A.
B.
The figure is a triangle. It is
The figure is a regular
not a regular polygon because triangle.
all sides and angles are not
congruent.
Course 2
18. 8-5 Classifying Polygons
Insert Lesson Title Here
Lesson Quiz: Part II
Determine whether each figure is a polygon. If
it in not, explain why not. Name each polygon.
4.
no; curved lines
5. Tell whether each figure above is a regular
polygon. If it is not, explain why not.
1: No, all sides and angles are not congruent.
2, 4: No, they are not polygons.
3: Yes
Course 2
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