8-5 Classifying Polygons Warm Up Problem of the Day Course 2 Warm Up Problem of the Day Lesson Presentation

8-5 Classifying Polygons Warm Up 1. How do you name a ray? Course 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°.

8-5 Classifying Polygons Problem of the Day Course 2 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 8-5 Classifying Polygons Learn to identify and name polygons.

Insert Lesson Title Here Course 2 8-5 Classifying Polygons Insert Lesson Title Here Vocabulary polygon regular polygon

8-5 Classifying Polygons Course 2 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 Vertex The polygon at left has six sides and six vertices. Vertices is plural for vertex. Remember!

Additional Example 1: Identifying Polygons Course 2 8-5 Classifying Polygons Additional Example 1: Identifying Polygons Determine whether each figure is a polygon. If it is not, explain why not. A. B. The figure is a polygon. It is a closed figure with 4 line segments. The figure is not a polygon. It is not a closed figure.

Additional Example 1: Identifying Polygons Course 2 8-5 Classifying Polygons Additional Example 1: Identifying Polygons Determine whether each figure is a polygon. If it is not, explain why not. C. D. The figure is not a polygon. The figure is not formed by line segments. The figure is not a polygon. There are line segments in the figure that intersect.

8-5 Classifying Polygons Check It Out: Example 1 Course 2 8-5 Classifying Polygons Check It Out: Example 1 Determine whether each figure is a polygon. If it is not, explain why not. A. B. The figure is a polygon. It is a closed figure with 5 line segments. The figure is not a polygon. It is not a closed figure.

8-5 Classifying Polygons Check It Out: Example 1 Course 2 8-5 Classifying Polygons Check It Out: Example 1 Determine whether each figure is a polygon. If it is not, explain why not. C. D. The figure is not a polygon. The figure is not formed by line segments. The figure is not a polygon. There are line segments in the figure that intersect.

8-5 Classifying Polygons Course 2 8-5 Classifying Polygons Polygons are classified by the number of sides and angles they have. Triangle 3 sides 3 angles Quadrilateral 4 sides 4 angles Pentagon 5 sides 5 angles Hexagon 6 sides 6 angles Heptagon 7 sides 7 angles Octagon 8 sides 8 angles Nonagon 9 sides 9 angles Decagon 10 sides 10 angles

Additional Example 2: Classifying Polygons Course 2 8-5 Classifying Polygons Additional Example 2: Classifying Polygons Name each polygon. A. B. Octagon Quadrilateral

Insert Lesson Title Here Course 2 8-5 Classifying Polygons Insert Lesson Title Here Check It Out: Example 2 Name each polygon. B. A. Quadrilateral Pentagon

Insert Lesson Title Here Course 2 8-5 Classifying Polygons Insert Lesson Title Here A regular polygon is a polygon in which all sides are congruent and all angles are congruent.

Additional Example 3: Identifying and Classifying Regular Polygons Course 2 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. B. A. The figure is a quadrilateral. It is not a regular polygon because all of the sides are not congruent. The figure is a regular quadrilateral. A regular quadrilateral is also called a square.

Insert Lesson Title Here Course 2 8-5 Classifying Polygons Insert Lesson Title Here Check It Out: Example 3 Name each polygon and tell whether it is a regular polygon. If it is not, explain why not. B. A. The figure is a triangle. It is not a regular polygon because all sides and angles are not congruent. The figure is a regular triangle.

Insert Lesson Title Here Course 2 8-5 Classifying Polygons Insert Lesson Title Here Lesson Quiz: Part I Determine whether each figure is a polygon. If it in not, explain why not. Name each polygon. 1. 2. 3. yes; pentagon no; open figure yes; octagon

Insert Lesson Title Here Course 2 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. 5. Tell whether each figure above is a regular t polygon. If it is not, explain why not. no; curved lines 1: No, all sides and angles are not congruent. 2, 4: No, they are not polygons. 3: Yes