Holt Geometry

1-6 Classify Polygons1-6 Classify Polygons

Holt Geometry

Warm UpWarm Up

Lesson PresentationLesson Presentation

Lesson QuizLesson Quiz

Holt Geometry

1-6 Classify Polygons

Warm Up

1. A ? is a three-sided polygon.

2. A ? is a four-sided polygon.

Evaluate each expression for n = 6.

3. (n – 4) 12

4. (n – 3) 90

Solve for a.

5. 12a + 4a + 9a = 100

triangle

quadrilateral

24

270

4

Holt Geometry

1-6 Classify Polygons

Classify polygons based on their sides and angles.

Find and use the measures of interior and exterior angles of polygons.

Objectives

Holt Geometry

1-6 Classify Polygons

side of a polygonvertex of a polygondiagonalregular polygonconcaveconvex

Vocabulary

Holt Geometry

1-6 Classify Polygons

Holt Geometry

1-6 Classify Polygons

Each segment that forms a polygon is a side of the polygon. The common endpoint of two sides is a vertex of the polygon. A segment that connects any two nonconsecutive vertices is a diagonal.

Holt Geometry

1-6 Classify Polygons

You can name a polygon by the number of its sides. The table shows the names of some common polygons.

Holt Geometry

1-6 Classify Polygons

A polygon is a closed plane figure formed by three or more segments that intersect only at their endpoints.

Remember!

Holt Geometry

1-6 Classify Polygons

Example 1A: Identifying Polygons

Tell whether the figure is a polygon. If it is a polygon, name it by the number of sides.

polygon, hexagon

Holt Geometry

1-6 Classify Polygons

Example 1B: Identifying Polygons

Tell whether the figure is a polygon. If it is a polygon, name it by the number of sides.

polygon, heptagon

Holt Geometry

1-6 Classify Polygons

Example 1C: Identifying Polygons

Tell whether the figure is a polygon. If it is a polygon, name it by the number of sides.

not a polygon

Holt Geometry

1-6 Classify Polygons

Check It Out! Example 1a

Tell whether each figure is a polygon. If it is a polygon, name it by the number of its sides.

not a polygon

Holt Geometry

1-6 Classify Polygons

Check It Out! Example 1b

Tell whether the figure is a polygon. If it is a polygon, name it by the number of its sides.

polygon, nonagon

Holt Geometry

1-6 Classify Polygons

Check It Out! Example 1c

Tell whether the figure is a polygon. If it is a polygon, name it by the number of its sides.

not a polygon

Holt Geometry

1-6 Classify Polygons

All the sides are congruent in an equilateral polygon. All the angles are congruent in an equiangular polygon. A regular polygon is one that is both equilateral and equiangular. If a polygon is not regular, it is called irregular.

Holt Geometry

1-6 Classify Polygons

A polygon is concave if any part of a diagonal contains points in the exterior of the polygon. If no diagonal contains points in the exterior, then the polygon is convex. A regular polygon is always convex.

Holt Geometry

1-6 Classify Polygons

Example 2A: Classifying Polygons

Tell whether the polygon is regular or irregular. Tell whether it is concave or convex.

irregular, convex

Holt Geometry

1-6 Classify Polygons

Example 2B: Classifying Polygons

Tell whether the polygon is regular or irregular. Tell whether it is concave or convex.

irregular, concave

Holt Geometry

1-6 Classify Polygons

Example 2C: Classifying Polygons

Tell whether the polygon is regular or irregular. Tell whether it is concave or convex.

regular, convex

Holt Geometry

1-6 Classify Polygons

Check It Out! Example 2a

Tell whether the polygon is regular or irregular. Tell whether it is concave or convex.

regular, convex

Holt Geometry

1-6 Classify Polygons

Check It Out! Example 2b

Tell whether the polygon is regular or irregular. Tell whether it is concave or convex.

irregular, concave