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Polygon Classification

Categories of polygons based on the number of sides.

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Polygon Classification

Let's Think About It

License: CC BY-NC 3.0

Monica pulls into a parking lot and sees a blue sign. She quickly recognizes the sign as a polygon, but she can't remember the exact name of the polygon. She stares at the sign for a few seconds then asks her younger sister to identify the shape. What type of polygon should her younger sister use to describe the sign?

In this concept, you will learn to classify polygons.

Guidance

A polygon is a simple closed figure formed by three or more segments. A triangle is a polygon and a quadrilateral is a polygon, too. Here are three pictures of polygons.

There are several different types of polygons.

Here is a list of the first eight types of polygons. 

1. A triangle has three sides.

2. A quadrilateral has four sides.

3. A pentagon has five sides.

4. A hexagon has six sides.

5. A heptagon has seven sides

6. An octagon has eight sides.

7. A nonagon has nine sides.

8. A decagon has ten sides.

Guided Practice

Classify the polygon that is represented in the picture.

License: CC BY-NC 3.0

First, count the number of sides for the television. Do not count the stand.

4

Then, classify the polygon.

Quadrilateral

The answer is that the television is shaped like a quadrilateral.

Examples

Classify the polygon that is represented in each picture. 

Example 1

First, count the number of sides.

8

Then, classify the polygon.

Octagon

The answer is that a Stop sign is shaped like an octagon.

Example 2

 

First, count the number of sides.

5

Then, classify the polygon.

5

The answer is that the Pentagon is shaped like a pentagon.

Example 3

 

First, count the number of sides for one of the shapes.

6

Then, classify the polygon.

Hexagon

The answer is a hexagon.

Follow Up

License: CC BY-NC 3.0

Remember Monica and the parking sign? She knows that the sign is a polygon, but she can't remember the name. She asks her younger sister. What type of polygon should her younger sister use to describe the shape of the sign?

First, count the number of sides.

4

Then, classify the polygon.

Quadrilateral

The answer is a quadrilateral. Her younger sister should describe the shape of the sign as a quadrilateral

Video Review

Explore More

Determine whether or not each image is a polygon. If yes, write polygon, if no, write not a polygon.

1.

2.

3.

4.

5.

6.

7.

8. A square tile on a floor

 For numbers 9 – 15, go back and use each figure in 1 – 7. Explain why it is or why it is not a polygon.

9.

10.

11.

12.

13.

14.

15.

Answers for Explore More Problems

To view the Explore More answers, open this PDF file and look for section 9.12. 

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Vocabulary

Concave

A concave polygon has at least one interior angle greater than 180 degrees. A common way to identify a concave polygon is to look for a "caved-in" side of the polygon.

Convex

A convex polygon contains no interior angles greater than 180 degrees.

Decagon

A decagon is a ten sided polygon.

Diagonal

A diagonal is a line segment in a polygon that connects nonconsecutive vertices

Exterior angles

An exterior angle is the angle formed by one side of a polygon and the extension of the adjacent side.

Heptagon

A heptagon is a seven sided polygon.

Hexagon

A hexagon is a six sided polygon.

Interior angles

Interior angles are the angles inside a figure.

Nonagon

A nonagon is a nine sided polygon.

Octagon

An octagon is an eight sided polygon.

Pentagon

A pentagon is a five sided polygon.

Polygon

A polygon is a simple closed figure with at least three straight sides.

Regular Polygon

A regular polygon is a polygon with all sides the same length and all angles the same measure.

Vertices

Vertices are points where line segments intersect.

Equilateral

A polygon is equilateral if all of its sides are the same length.

Image Attributions

  1. [1]^ License: CC BY-NC 3.0
  2. [2]^ License: CC BY-NC 3.0
  3. [3]^ License: CC BY-NC 3.0

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