## Boarding of Symmetrical Shapes

### Janet GreathouseBay District Schools

#### Description

The students use geoboards to model polygons and to practice finding lines of symmetry.

#### Objectives

The student understands the concepts of spatial relationships, symmetry, reflections, congruency, and similarity.

#### Materials

-Computer(s) with Internet capability to access the online student lesson, Let's Learn Symmetry, available from the Beacon Learning Center
-Geoboards and bands
-Geoboard grid worksheet (available in most textbook resource kits)
-Mirrors
-Chart paper
-Math journals

#### Preparations

1. Make sure all computers are online or bookmarked to Let's Learn Symmetry. (See Weblinks.)
2. Have geoboards and rubberbands ready.
3. Copy geoboard grids for students or groups of students.
4. Gather mirrors.
5. Create a class chart as detailed in step six of the lesson procedures.

#### Procedures

PREREQUISITES:

a. Students know how to create various types of polygons: triangles, quadrilaterals, pentagons, hexagons, etc.
b. Students have completed the Beacon Student Web Lesson: Let's Learn Symmetry.

1. Pass out the geoboards to students or groups of students (no more than four students in each group).

2. Demonstrate how to make a polygon using the overhead geoboard and a band. Then use a different colored band to show students the line or lines of symmetry.

3. Demonstrate several other examples and how to determine the line or lines of symmetry. Select polygonal examples that will show zero, one, two, and three lines of symmetry (horizontal, vertical, and diagonal).

4. Next, one student chooses to make a triangle, a quadrilateral such as a trapezoid, a pentagon, or a hexagon using the group's geoboard and bands. He or she then trades with a partner to see if they can find the line(s) of symmetry. The students record the polygon and its line(s) of symmetry on the geoboard grid worksheet provided by the teacher. (Remind students to use one rubber band to model each polygon and a different colored band to show the line or lines of symmetry.)

5. As a class, discuss which types of triangles, quadrilaterals, and other polygons have 0, 1, 2, or more lines of symmetry. You may want to provide small mirrors so that students can see the mirror image of one side of the symmetrical figures.

6. Students use their geoboard grids to help complete a class chart of symmetrical shapes during center time. Label the chart paper with the following three columns:
(a) Polygon created (name)
(b) Shape (drawn by the students)
(c) Number of Lines of Symmetry

7. After completing the class chart, ask students to write down in their journals any patterns they see between the shapes drawn and the lines of symmetry identified. Use journal responses to guide further teaching lessons and additional concrete explorations with symmetry.

#### Assessments

Formative Assessment

Use the students' geoboard grids and journal entries to assess what they know about symmetry. Students should be able to use the concrete materials and grid to accurately show and record line(s) of symmetry. Their writings should reflect a comprehension of symmetry based on the classroom experiences.