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

Course 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°.

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 Classifying Polygons

Learn to identify and name polygons. Course Classifying Polygons

Vocabulary polygon regular polygon Insert Lesson Title Here Course Classifying 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. Triangles and rectangles are examples of polygons. The polygon at left has six sides and six vertices. Vertices is plural for vertex. Remember! Side Vertex Course Classifying Polygons

Determine whether each figure is a polygon. If it is not, explain why not. Additional Example 1: Identifying Polygons 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. Course Classifying Polygons

Determine whether each figure is a polygon. If it is not, explain why not. Additional Example 1: Identifying Polygons 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. Course Classifying Polygons

Determine whether each figure is a polygon. If it is not, explain why not. Check It Out: Example 1 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. Course Classifying Polygons

Determine whether each figure is a polygon. If it is not, explain why not. Check It Out: Example 1 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. Course 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 Course Classifying Polygons

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

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

Insert Lesson Title Here A regular polygon is a polygon in which all sides are congruent and all angles are congruent. Course 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. The figure is a regular quadrilateral. A regular quadrilateral is also called a square. The figure is a quadrilateral. It is not a regular polygon because all of the sides are not congruent. A. B. Course Classifying Polygons

Check It Out: Example 3 Insert Lesson Title Here 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. Name each polygon and tell whether it is a regular polygon. If it is not, explain why not. A. B. Course Classifying Polygons

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

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