Illuminations: Investigating Shapes (Triangles)

Investigating Shapes (Triangles)

Making Virtual Triangles

In this lesson, students use virtual manipulatives to explore triangles. They create virtual representations of triangles on an electronic geoboard. They also identify shapes within shapes using tangrams. This activity is appropriate for a computer lab, so all students have access to the virtual manipulatives.

Learning Objectives
 
Students will:
  • identify and recognize triangles using multiple representations
  • construct triangles

Materials
 
Making Triangles Tool
Geoboards Activity Sheet

Instructional Plan

Review properties of triangles by having students share the recordings they made in the previous session.

Invite students to the computer area and demonstrate how to create triangles using Making Triangles Tool.

Making Triangles Tool Making Triangles Tool

Guide students through the steps of clicking and dragging geobands to the geoboards to create triangles with three corners (angles). Remind students how to create a triangle on a real geoboard and that the number of sides of a triangle does not change.

 

 

Instruct students to create at least five different triangles and to copy these triangles on their Geoboards activity sheets.

Geoboards Activity Sheet Geoboards Activity Sheet

Specifically, you may ask students to create triangles with particular traits. Depending upon students' experiences with triangles, they could create triangles with:

  • all 3 sides different lengths
  • 2 sides the same length
  • all 3 sides the same length (although this may be a challenge for some)
  • one right angle
  • etc.

Then students can record their examples on the Geoboards activity sheet.

Questions for Students
 

Can you tell me how many sides each triangle has?

[A triangle has 3 sides.]

Describe the different kinds of triangles you made. How are they alike? How are they different?

[They are alike because they all have different sides. They are different because they are different sizes. ]

Assessment Options
 
  1. Record your observations of students’ work and comments on the teacher resource sheet Class Notes.
  2. Collect students' Geoboard activity sheets to assess students' pictorial representations of triangles.

Extensions
 
  1. When students have finished creating and copying their triangles, have them go to the Tangram Game at the PBS Kids Web site’s Sagwa section. The game allows students to work at varying levels of difficulty while using a drag-and-drop feature to drag tangrams to complete an outlined picture or “fill in” a picture.

Teacher Reflection
 
  • Which strategies worked well with the students? Which stratgies did not work well?
  • Which ideas did the students give you that will influence how you teach this lesson next time or reinforce the objectives of this lesson later in the school term as a review?
  • What key vocabulary words did I use in the triangle lessons? Do students understand what these vocabulary words mean?"

NCTM Standards and Expectations
 
Geometry Pre-K-2
  1. Recognize, name, build, draw, compare, and sort two- and three-dimensional shapes .
  2. Recognize and represent shapes from different perspectives.
This lesson prepared by Carol Midgett.
  
1 period   

NCTM Resources

Principles and Standards for School Mathematics
National Council of Teachers of Mathematics Thinkfinity Verizon Foundation
More and Better Mathematics for All Students
© 2000 National Council of Teachers of Mathematics
Use of this Web site constitutes acceptance of the Terms of Use

The National Council of Teachers of Mathematics is a public voice of mathematics education, providing vision, leadership, and professional development to support teachers in ensuring mathematics learning of the highest quality for all students. The views expressed or implied, unless otherwise noted, should not be interpreted as official positions of the Council.