8 5 Classifying Polygons Warm Up Problem of

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

8 -5 Classifying Insert Lesson Title Here Polygons Vocabulary polygon regular polygon 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 The polygon at left has six sides and six Vertex vertices. Remember! Vertices is plural for vertex. 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. 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 -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.

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.

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.

8 -5 Classifying 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

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

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

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

8 -5 Classifying Insert Lesson Title Here 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

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

8 -5 Classifying Insert Lesson Polygons 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 t