5E Lesson Plan

Lines of Symmetry

teachHOUSTON Student Name:
Mentor Teacher Name:
Lesson Teaching Date:

Grade Level: 4th

Concept(s): An figure is symmetrical if the figure is capable of being divided by a line into 2 parts that are reflections of each other. A figure can have zero, one, or multiple lines of symmetry. Artwork is often symmetrical and even the human body is symmetrical. The field of architectures also uses the rules of symmetry in the construction of bulidings.
TEKS: 4.9 Geometry and spatial reasoning. The student connects transformations to congruence and symmetry. (C) Use reflections to verify that a shape has symmetry.

Objectives The student will be able to:	Evaluation Question for each Objective
1. Use reflections to determine whether a figure has line symmetry.
2. Identify the number of lines of symmetry a figure has and draw them on a figure.
3. Construct a figure with a given number of lines of symmetry.

Material List and Advanced Preparations:
For each student:

A mirror
“Symmetry with Polygons” Activity Sheet

For each pair of students:

An envelope with two pictures inside: one with line symmetry and the other without (use logos, pictures of stop signs, red lights, magazine clippings)

For each group:

Set of shapes (rectangle, parallelogram, octagon, triangle, regular hexagon, hexagon, pentagon, rhombus, trapezoid, and right triangle)
Pattern Blocks

Advanced Preparations:

Create a transparency of “The Raggles and the Fraggles”
Make copies of Evaluation and “Lines of Symmetry” handout

ENGAGEMENT
What the Teacher Will Do	Eliciting Questions/ Student Responses	What the Students Will Do
Display “The Raggles and the Fraggles” transparency on the overhead	What is something that all Raggles have in common? They look even They are the same on both sides They look more normal What is something that all Fraggles have in common? They look lop-sided They are crooked They are not the same on both sides There is a mathematical name for shapes that look like Raggles. What is it? Symmetrical Can you think of anything in real life that is symmetrical? My face My desk The chalkboard	Students will examine the examples of Raggles and Fraggles and brainstorm possible criteria for each type of figure.
Group the students in pairs and give each pair an envelope which contains two pictures: one that has line symmetry and another that does not.	How do you know that your picture is symmetrical? If I fold it in half, both sides are the same, just opposite Can a figure have more than one line of symmetry? yes Does anyone have a picture that has more than one line of symmetry? How did you know it has more than one line of symmetry? You can fold it in half horizontally or vertically (or diagonally) and it is the same on both sides	Each pair of students will decide which picture has symmetry and which does not. Pairs of students will present their pictures and explanations to the class.

TRANSITION

Polygons of all sorts can also have lines of symmetry. Now you are going to find lines of symmetry of shapes.

EXPLORATION

What the Teacher Will Do

Eliciting Questions/
Student Responses

What the Students Will Do

Divide the class into groups of four and pass out a “Lines of Symmetry” handout to each student.

The teacher will demonstrate how to use the mirror to find a line of symmetry. Put a diagram of a rectangle and a parallelogram on the overhead. Show students what happens when you use the mirror on each shape.

The teacher will monitor students’ progress as they work in groups.

Where do you think an axis of symmetry might be in a rectangle?
In the middle horizontally
In the middle vertically

What is reflected in the mirror when you find an axis of symmetry?
The same shape

How many lines of symmetry does the rectangle have?
two

Where do you think an axis of symmetry might be in a parallelogram?
On the diagonal

What is reflected in the mirror when you place it on the diagonal of a parallelogram?
A different shape

What can we conclude about a parallelogram?
It doesn’t have a line of symmetry

Students will use a mirror to find all the lines of symmetry on 10 different polygons. Students will name each polygon and draw in the lines of symmetry on each figure.

TRANSITION

Now you will have an opportunity to share the lines of symmetry you found with the class.

EXPLANATION

What the Teacher Will Do

Eliciting Questions/
Student Responses

What the Students Will Do

Facilitate a class discussion surrounding the results of students’ exploration.

Does this polygon have symmetry?

How many lines of symmetry does it have?

Do you notice a pattern in the number of lines of symmetry a polygon has?
No, sometimes two of the same shape have different lines of symmetry. For example, #1 and #2 are both triangles, but one has symmetry and one doesn’t.

Which polygons have the same number of lines of symmetry as the number of sides?
triangle, square, hexagon

What is true about these polygons?
Their sides are the same length

Selected students will present their lines of symmetry to the class.

TRANSITION

You have found the lines of symmetry in given polygons. Now you are going to create your own shapes with symmetry.

ELABORATION

What the Teacher Will Do

Eliciting Questions/
Student Responses

What the Students Will Do

Give each pair of students a set of pattern blocks.

Students will use pattern blocks to complete the following tasks:

Create a shape with exactly 1 line of symmetry
Create a shape with no lines of symmetry
Create a shape with 2 lines of symmetry
Create a shape with more than 2 lines of symmetry
Create a symmetrical shape. Can you move one of the blocks and keep your shape symmetrical?

TRANSITION

Now you will get a chance to show what you have learned today.

EVALUATION

An evaluation instrument is to be created. It should have at least 3 questions. Identify one lesson objective that matches each question.

Name: ______________

Lines of Symmetry of Polygons
Use the mirror to find all the lines of symmetry for each shape. Draw in the lines of symmetry on each shape and complete the table.

The Raggles and the Fraggles

Here are some examples of a Raggle.

What is the difference between a Raggle and a Fraggle?