7-5 Polygons Learn to identify and name polygons. Course 2 7-5 Polygons Insert Lesson Title Here Vocabulary polygon side vertex of a polygon regular polygon Course 2 7-5 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 7-5 Polygons Additional Example 1A & 1B: 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. 7-5 Polygons Additional Example 1C & 1D: 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 cross. 7-5 Polygons Try This: Example 1A & 1B 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. 7-5 Polygons Try This: Example 1C & 1D 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 cross. 7-5 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 7-5 Polygons Additional Example 2: Classifying Polygons Name each polygon. A. B. Octagon Course 2 Quadrilateral 7-5 Insert Lesson Title Here Polygons Try This: Example 2 Name each polygon. B. A. Quadrilateral Course 2 Pentagon 7-5 Insert Lesson Title Here Polygons A regular polygon is a polygon in which all sides are congruent and all angles are congruent. Course 2 7-5 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. 7-5 Insert Lesson Title Here Polygons Try This: 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 7-5 Polygons Insert Lesson Title Here Lesson Quiz Determine whether each statement is true or false. 1. Every polygon is a closed figure. true 2. Every open figure is a polygon. false 3. A pentagon with sides lengths of 10 units and angles measuring 108° is a regular polygon. true 4. A quadrilateral with side lengths of 10, 12, 10, and 12 units is a regular polygon. false 5. What is the name of a five-sided polygon? pentagon Course 2 Homework 7-5 Worksheet
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