Illuminations: Investigating the Concept of Triangle and the Properties of Polygons

Investigating the Concept of Triangle and the Properties of Polygons


Creating Polygons

In Creating Polygons, students make and compare a variety of polygons, describing the salient properties of the shapes they create. Both lessons in this two-part unit help students reach the goals described in the Geometry Standard.

Learning Objectives

 

Students will

  • make and compare a variety of polygons, describing the salient properties of the shapes they create.

Materials

 
  • Computer and Internet connection

Instructional Plan

Task

Make these figures on the geoboard:

  • As many different-sized squares as possible
  • Many different hexagons
  • The polygon with the fewest number of sides
  • The polygon with the largest number of sides you can make
  • Polygons with every number of sides between the fewest and the largest

[How to Use the Interactive Figure]

[Stand-alone applet]

Learning about Polygons in the Classroom

Through small-group or informal class discussions, teachers help students learn geometric vocabulary as well as learn about properties of different polygons. Some properties of figures will be easier to identify than others as students plan how to create a figure on a geoboard. For example, polygons are made with straight lines, as modeled by a band connecting two nodes, and polygons are closed figures. Students can learn the names of the specific figures they create as they talk about the hexagons that have six sides and the quadrilaterals that have four sides.

Students can make their favorite polygon on a geoboard and describe it to the class. Teachers might ask if any figures are congruent and how students might justify their claims. Students can sort the polygons and describe why they are grouped in certain ways.

Working with interactive computer geoboards make exploring polygons easy for students who have difficulty managing the rubber bands. Because students have a broad work space, they can make a large variety of polygons. There is room to create multiple convex and concave figures, and they can view all of them at once. Filling the polygons with color helps young students notice the number of sides and, because open figures cannot be shaded, reinforces the understanding that polygons are closed figures. As with physical geoboards, the lines created by the bands are straight, not curved.

Teacher Reflection

 
  • What experiences, knowledge, and vocabulary should students have in order to develop an understanding of properties of polygons?

NCTM Standards and Expectations

 
Geometry Pre-K-2
  1. Recognize, name, build, draw, compare, and sort two- and three-dimensional shapes .
  
1 period   

NCTM Resources

Principles and Standards for School Mathematics


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