Illuminations: Investigating Shapes (Triangles)

# Investigating Shapes (Triangles)

Recognizing and understanding the properties of triangles and their positions in space are foundational to young studentsâ€™ knowledge of geometry. In these lessons, students identify characteristics of triangles, manipulate electronic geoboards to construct triangles, and name the trianglesâ€™ relative locations. In addition, through music and observation, students identify triangles in their environment. These lessons are especially appropriate for students in prekindergarten and kindergarten.

These lessons comprise a series of learning experiences. For students to fully understand the concepts presented here, it is recommended that these lessons be included in a more fully developed Standards-based unit on geometry rather than used as stand-alone lessons.

### Math Content

• Students will identify and recognize triangles using multiple representations.
• Students will locate triangles in their environment.
• Students will construct triangles using both concrete and electronic tools.

### Individual Lessons

Lesson 1 - Three Sides

In this lesson, students compare and contrast shapes using attribute blocks. Because the equilateral triangle (a triangle with congruent sides and congruent angles) is the most common example used in textbooks and other reference materials, this is an important opportunity for you to help students realize that other triangles exist and that triangles can have angles of different measures. The lesson is designed to accommodate multiple learning styles and intelligences.

Lesson 2 - Tracing and Drawing

In this lesson, students continue to discuss attributes of triangles. They trace and draw triangles individually. Students recognize objects in their environment that are shaped like triangles and explain to the class how they recognized the shape.

Lesson 3 - Geoboards

Students use appropriate vocabulary to describe shapes to their classmates. Students focus on the properties of shapes to develop mental images of objects from descriptors. They create multiple representations of triangles using geoboards, string, and crayons and paper.

Lesson 4 - 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.

### NCTM Resources

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