# Understanding lines of symmetry in mathematics Primary 3 Mathematics Third Term Lesson Notes Week 9

### Lesson Plan Presentation: Line(s) of Symmetry, Properties of Square, Rectangle, and Triangle, Curve and Straight Lines

Subject: Mathematics

Term : Third Term

Week : Week 9

Topic : Properties of squares, rectangles, and triangles explained, Meaning of lines of Symmetry

Duration: 60 minutes

### Learning Objectives:

1. Understand the concept of symmetry and identify lines of symmetry in different shapes.
2. Identify and describe the properties of squares, rectangles, and triangles.
3. Differentiate between curves and straight lines.
4. Recognize the importance of symmetry, curves, and straight lines in practical applications such as bricklaying and carpentry.

### Embedded Core Skills:

1. Critical thinking: Analyzing and identifying lines of symmetry in shapes.
2. Geometry: Understanding the properties of squares, rectangles, and triangles.
3. Visual perception: Differentiating between curves and straight lines.
4. Practical application: Relating the concepts to real-life professions like bricklaying and carpentry.

### Learning Materials:

• Chart paper and markers
• Geometric shapes cutouts (squares, rectangles, triangles)
• Drawing paper and pencils
• Ruler
• Real-life pictures of curved and straight lines
• Construction materials (blocks, wooden boards) for hands-on activities
• MathIsFun – Symmetry Section: https://www.mathsisfun.com/geometry/symmetry.html
• This website provides interactive explanations and activities to help students understand symmetry.

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### Content

Good morning, class! Today, we’re going to learn about some interesting topics in mathematics. We’ll start by discussing the concept of symmetry, then move on to the properties of squares, rectangles, and triangles. Finally, we’ll explore the difference between curves and straight lines.

Let’s begin with symmetry. Symmetry is a fascinating aspect of mathematics that deals with balance and reflection. Symmetry exists when a shape or object can be divided into two equal parts that match each other perfectly. We call this line of division the line of symmetry.

Now, let’s talk about the importance of symmetry in practical applications. Bricklayers use the knowledge of symmetry to set blocks accurately. When constructing a wall, they need to ensure that the blocks are aligned and symmetrically placed, which creates a stable and visually appealing structure.

Similarly, carpenters rely on symmetry in their work, especially in carpentry and joinery. They need to create symmetrical designs, such as matching cabinets or doors, for aesthetic purposes. By understanding symmetry, carpenters can achieve balance and precision in their craft.

Moving on to the properties of squares, rectangles, and triangles. These are all common shapes that have unique characteristics.

A square is a four-sided polygon with all sides of equal length and all angles equal to 90 degrees. Its properties include having four lines of symmetry, which means it can be divided into four equal parts that are mirror images of each other. A square also has diagonals that bisect each other at right angles.

A rectangle is another four-sided polygon, but unlike a square, its opposite sides are of equal length, and all angles are equal to 90 degrees. It has two lines of symmetry, dividing it into two equal halves. Rectangles also have diagonals that bisect each other, but they are not necessarily equal in length.

Lastly, we have triangles, which are three-sided polygons. Triangles can have different properties based on their side lengths and angles. For example, an equilateral triangle has all sides and angles equal, while an isosceles triangle has two equal sides. Triangles can also be classified based on their angles as acute, obtuse, or right triangles.

Now, let’s discuss the difference between curves and straight lines. A straight line is the shortest distance between two points and remains the same throughout its length. It has no curves or bends. Straight lines are used extensively in construction, engineering, and various other fields to ensure accuracy and precision in measurements and designs.

On the other hand, curves refer to lines that are not straight and have bends or arcs. Curves are commonly found in nature, art, and architecture. They add aesthetic appeal and can create a sense of movement or flow. Understanding curves is essential for artists, designers, and architects, as they often work with organic and flowing shapes.

In conclusion, the concepts of symmetry, the properties of squares, rectangles, and triangles, and the distinction between curves and straight lines are important in various practical applications. Bricklayers and carpenters utilize symmetry to create stable and visually pleasing structures, while straight lines are crucial for accurate measurements and designs. Curves, on the other hand, offer aesthetic appeal and are often used in artistic and architectural creations. Understanding these concepts can help us appreciate the mathematical principles behind everyday tasks and professions.

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Lines of Symmetry

• Symmetry deals with balance and reflection.
• Symmetry exists when a shape can be divided into two equal parts that match each other perfectly.
• The line of division is called the line of symmetry.
• Bricklayers use symmetry to set blocks accurately.
• Carpenters rely on symmetry for creating symmetrical designs in carpentry and joinery.

Properties of Square:

• A square is a four-sided polygon.
• All sides of a square are equal in length.
• All angles of a square are equal to 90 degrees.
• A square has four lines of symmetry.
• The diagonals of a square bisect each other at right angles.

Properties of Rectangle:

• A rectangle is a four-sided polygon.
• Opposite sides of a rectangle are equal in length.
• All angles of a rectangle are equal to 90 degrees.
• A rectangle has two lines of symmetry.
• The diagonals of a rectangle bisect each other, but they are not necessarily equal in length.

Properties of Triangle:

• A triangle is a three-sided polygon.
• Triangles can have different properties based on side lengths and angles.
• An equilateral triangle has all sides and angles equal.
• An isosceles triangle has two equal sides.
• Triangles can be classified based on angles as acute, obtuse, or right triangles.

Difference between Curves and Straight Lines:

• A straight line is the shortest distance between two points and remains the same throughout its length.
• Straight lines are used for accurate measurements and designs.
• Curves refer to lines that are not straight and have bends or arcs.
• Curves are used for aesthetic appeal and can be found in nature, art, and architecture.
• Artists, designers, and architects work with curves to create organic and flowing shapes.

Importance:

• Bricklayers use symmetry to set blocks accurately.
• Carpenters rely on symmetry for creating symmetrical designs.
• Straight lines are crucial for accurate measurements and designs in various fields.
• Curves add aesthetic appeal and are used in art and architecture

Evaluation

1. A square has _______ lines of symmetry. a) 1 b) 2 c) 4
2. An isosceles triangle has _______ lines of symmetry. a) 0 b) 1 c) 2
3. A rectangle has _______ lines of symmetry. a) 1 b) 2 c) 4
4. A curve is a line that has _______. a) bends or arcs b) no bends or arcs c) straight segments only
5. Straight lines are important in _______. a) construction b) art c) gardening
6. A square has _______ angles. a) 60 degrees b) 90 degrees c) 120 degrees
7. An equilateral triangle has _______ lines of symmetry. a) 0 b) 1 c) 3
8. Carpenters use the knowledge of symmetry in _______. a) plumbing b) carpentry and joinery c) electrical works
9. A right triangle has _______ angle(s) measuring 90 degrees. a) 1 b) 2 c) 3
10. The importance of symmetry for bricklayers is in _______. a) setting blocks accurately b) painting walls c) creating sculptures

Presentation:

1. Introduction (5 minutes)
• Greet the students and briefly explain the topics to be covered.
• Share the importance of the concepts in bricklaying and carpentry.
2. Line(s) of Symmetry (10 minutes)
• Define symmetry and explain the concept of lines of symmetry.
• Present examples of shapes with lines of symmetry, such as squares, rectangles, and triangles.
• Discuss how bricklayers use symmetry to set blocks accurately and carpenters in their work.
• Engage students in a discussion by asking questions and encouraging participation.
3. Properties of Square, Rectangle, and Triangle (15 minutes)
• Present each shape individually, highlighting their properties.
• Demonstrate the properties of a square, including equal sides, 90-degree angles, and four lines of symmetry.
• Discuss the properties of a rectangle, such as opposite sides being equal, 90-degree angles, and two lines of symmetry.
• Describe the properties of a triangle, differentiating between equilateral, isosceles, and right triangles.
• Provide examples and encourage students to identify these shapes and their properties.
4. Curve and Straight Lines (10 minutes)
• Explain the difference between curves and straight lines.
• Show real-life pictures of curved and straight lines to enhance understanding.
• Discuss how straight lines are used in construction and other fields.
• Discuss the aesthetic appeal of curves in art and architecture.
5. Teacher’s Activities (10 minutes)
• Engage students in a hands-on activity by providing construction materials (blocks, wooden boards).
• Ask students to create shapes with lines of symmetry using the materials.
• Encourage them to experiment with curves and straight lines in their designs.
• Monitor their activities and provide guidance as needed.
6. Learners’ Activities (10 minutes)
• Students work individually or in small groups to complete worksheets or drawing activities.
• Worksheets can include identifying lines of symmetry, properties of shapes, and distinguishing between curves and straight lines.
7. Assessment (5 minutes)
• Conduct a class discussion to assess students’ understanding.
• Ask questions related to the topics covered and encourage students to answer.
• Provide immediate feedback and clarification as necessary.
8. Evaluation Questions:
1. How many lines of symmetry does a square have?
2. What are the properties of a rectangle?
3. Name an example of a curved line in real life.
4. How do bricklayers use the knowledge of symmetry?
5. What is the importance of straight lines in construction?
6. Can you identify the lines of symmetry in an equilateral triangle?
7. Describe the properties of an isosceles triangle.
8. Give an example of a profession where knowledge of curves is important.
9. What is the practical application of understanding symmetry in carpentry?
10. How can you differentiate between a curve and a straight line?

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1. Conclusion (5 minutes)
• Recap the key points covered in the lesson, including lines of symmetry, properties of squares, rectangles, and triangles, and the difference between curves and straight lines.
• Emphasize the importance of these concepts in real-life professions such as bricklaying and carpentry.
• Encourage students to explore and appreciate symmetry, shapes, and lines in their surroundings.
2. Homework (optional)
• Assign a task where students observe their environment and identify examples of symmetry, curves, and straight lines.
• They can create a small presentation or a collage to showcase their findings.

Note: Adapt the duration and activities as per the needs of your class and available resources.

Remember to be interactive, encourage participation, and provide positive reinforcement throughout the lesson.

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