Let’s Learn!
How do you define and identify polygons?
Goal:
Goal:
Think About It!
Goal: Define and identify polygons.
Ava sees the beautiful tapestry hanging. She notices many shapes.
Many of the shapes she sees are called polygons. A polygon is a closed, 2-dimensional shape formed by 3 or more straight sides. A polygon cannot have curved sides. The straight sides come together at a vertex and form an angle. So a polygon has at least 3 straight sides and at least 3 angles.
As Ava explores the shapes in the tapestry, she will ask herself these three questions to figure out if the shapes are polygons.
- Is the shape closed?
- Is the shape 2-dimensional?
- Does the shape have 3 or more straight sides?
Click through the slides below to learn about the polygons Ava sees.
Ava takes a closer look at the tapestry. She wonders how to know if the circle is a polygon.
She thinks about the definition of a polygon and decides to ask herself these questions as she looks at the circle. Can you help? Think of the answer to each question. Then, click the question to check your answer.
Yes, it is a closed shape.
Yes, it is flat.
No, a circle does not have straight sides.
Since a polygon is a closed, 2-dimensional shape formed by 3 or more straight sides, a circle cannot be a polygon!
Let’s see what other shapes Ava finds. Are they polygons? Ask yourself the three questions to determine if they are polygons. Then, click the shapes to see if you are right. Remove the shapes you have viewed by clicking remove. Continue after completing all the cards.
Triangle
Yes. A triangle is a polygon. It is a closed shape, it is 2-dimensional, and there are 3 straight sides.
Quadrilateral
Yes. A quadrilateral is a polygon. It is a closed shape, it is 2-dimensional, and there are 4 straight sides.
Pentagon
Yes. A Pentagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 5 straight sides.
Hexagon
Yes. A hexagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 6 straight sides.
Heptagon
Yes. A heptagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 7 straight sides.
Octagon
Yes. A octagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 8 straight sides.
Nonagon
Yes. A nonagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 9 straight sides.
Decagon
Yes. A decagon is a polygon. It is a closed shape, it is 2-dimensional, and there are 10 straight sides.
In your notes, draw and label the polygons above. Make sure to write down how many sides each polygon has. Now use the three questions about polygons to answer these questions.
Question!
Is this shape a polygon?
No, this is not a polygon. It is a closed shape and is 2-dimensional, but not all of the sides are straight!
Is this shape a polygon?
Yes! This shape is closed, is 2-dimensional, and has six sides and six angles.
Ava decides to organize what she notices about the polygons in a chart. Look at the name and number of sides of each polygon. Compare your notes to hers.
| Triangle | \({=}\) | 3 sides |
| Quadrilateral | \({=}\) | 4 sides |
| Pentagon | \({=}\) | 5 sides |
| Hexagon | \({=}\) | 6 sides |
| Heptagon | \({=}\) | 7 sides |
| Octagon | \({=}\) | 8 sides |
| Nonagon | \({=}\) | 9 sides |
| Decagon | \({=}\) | 10 sides |
Ava thinks she sees a pattern in the number of sides and the number of angles. Let’s count the angles to find a pattern. Click on the shape to see!
| Name | Triangle | Quadrilateral | Pentagon | Hexagon |
|---|---|---|---|---|
| Sides | ||||
| Angles |
| Name | Heptagon | Octagon | Nonagon | Decagon |
|---|---|---|---|---|
| Sides | ||||
| Angles |
What do you notice about the number of sides and the number of angles? Click the Show Me button to see the pattern!
The number of sides and the number of angles are the same!
Question
What kind of polygon is this?
This shape has five sides and five angles. It is a pentagon.
Ava wants to see some more polygons in the world around her. Let’s follow her!