1. Learning Objectives In this session, Mathematicians will: O Broaden your thinking about polygons. O Classify polygons according to some of their features. O Understand how to divide polygons into triangles and the implications of that. O Begin to understand mathematical definitions.

2. Comparing Triangles and Quadrilaterals TriangleQuadrilateral

3. Revisiting some properties of Quadrilaterals On your geoboard, create the following quadrilaterals: O Square O Rectangle O Trapezium O Rhombus

4. Defining Polygons O All of these shapes have similar features. O That these shapes do not have. O List the features that the top group of shapes have in common. Features -

5. Classification of Polygons

6. Polygons with more than 10 sides are not usually given special names. A polygon with 11 sides is described as an 11-gon, a polygon with 12 sides as a 12-gon, and so on. Each of the polygons above is a 17-gon. When people talk about a general polygon -- one where you don't know the exact number of sides -- they often refer to it as an n-gon. What name did you think is given to each of these shapes? Each shape has the same number of sides.

7. Polygons The polygons have been put into the following categories. What could the labels for the categories be?

8. Polygon Classification O Polygons can be grouped into various classes: Concave, Regular, Symmetry

9. Polygon Classification O Polygons can be grouped into various classes: Concave, Regular, Symmetry

10. Polygon Classification O Polygons can be grouped into various classes: Concave, Regular, Symmetry

11. Polygons What would the diagram look like to show how these same four polygons can be grouped into the categories: Line Symmetry and Not Concave.

12. Polygons What would the diagram look like to show how these same four polygons can be grouped into the categories: Line Symmetry and Not Concave.

13. Grouping Polygons – All As a warm-up for the game, put each of the labels Regular, Concave, and Triangle next to one of the circles on the diagram. Place all the polygons in the correct regions of the diagram.on the diagrampolygons Regular TriangleConcave

14. Grouping Polygons – All As a warm-up for the game, put each of the labels Regular, Concave, and Triangle next to one of the circles on the diagram. Place all the polygons in the correct regions of the diagram.on the diagrampolygons

15. Grouping Polygons – Task A You have been given a Venn Diagram with shapes already placed in it. Determine which labels should go on each circle of the Venn diagram.

16. Grouping Polygons – Task B O The leader selects three category cards and looks at them without showing them to the other group members. O The leader uses the cards to label the regions, placing one card face down next to each circle. O The other group members take turns selecting a polygon, and the leader places the polygon in the correct region of the diagram. O After a player's shape has been placed in the diagram, he or she may guess what the labels are. The first player to guess correctly wins. O Take turns being the leader until each member of the group has had a chance.

17. Reflection O What were some of your strategies for determining the labels for each of the categories? O What were some of your challenges with each task.