Lesson 3: Polygon Attributes


Activity 1: Polygon Parts

Materials: The Greedy Triangle by Marilyn Burns, colored pencils or markers, construction paper (kit), fine point dry-erase marker (kit), geoboard (kit), glue, Interactive Notebook (kit), rubber bands (kit), scissors, whiteboard (kit)
Draw two four-sided shapes on a whiteboard: one that is closed (all the sides are connected) and one that is open (two of the sides are not connected). Ask your child to identify which one is a polygon, and explain why (the one that is closed because all polygons are closed).

Look back through the pages of The Greedy Triangle, and ask your child if he remembers what the shape asked for each time it wanted to become something new. Reread a couple of the pages as needed, focusing on the line "I think if I had just one more side and one more angle."
Create a large triangle on a geoboard, and explain that this polygon has three parts: sides, angles, and vertices. Ask your child to identify its sides. Ask: "How many sides does a triangle have?" (3) Now ask your child to identify its angles. If he can't do so, point to one of them (the space created where two sides meet), and ask him to point to the other two. Now help him identify the vertices. Say "vertex" as you point to each one. Explain that these are the points where the sides meet and that a triangle has three of them. Also explain that we say "one vertex" and "two or more vertices" as "vertices" is the word to use for more than one. Ask your child to explain each of these three parts in his own words: "How would you tell someone else what a side, an angle, and a vertex are on a polygon?"

Now, tell your child to create a large square on the geoboard and ask him to identify its sides, angles, and vertices. How many does it have of each?

Using the "Polygon Parts" sheet, ask your child to cut out the large pentagon, the title, and the following words along the dotted lines: "Polygon Parts," "Side," "Angle," and "Vertex." He will color the pentagon and the words using different colors. Next, he will glue the pentagon onto a piece of construction paper and glue the words where they go to show the parts of a polygon. Finally, he will glue the title, "Polygon Parts," at the top of the page. Store this sheet in his Interactive Notebook so that he can refer back to it as needed.

Activity 2: Counting Polygon Parts

Your child will complete the "How Many Parts" sheet by filling in the table provided to show how many sides, angles, and vertices each of the polygons on the sheet has. When he's finished, ask him if he notices any patterns about the parts of polygons. He should note that polygons always have the same number of sides, angles, and vertices. Ask: "How many of each part do you think a circle has?" (only one side and it's curved)
"How Many Parts" Answer Key