Class: Senior Secondary School 1 (SS1, SS 1, SSS1, SSS 1)
Term: Second Term
Week: 2
Age: 15 years
Duration: 45 minutes
Subject: Technical Drawing
Curriculum Theme: Technical Drawing
Previous Lesson: Polygons: Definition, Types and Properties.
Topic: POLYGONS
Subject Matter: construction of regular polygons, square method of polygon construction, circle method of polygon construction, diagonal method of polygon construction, accurate instrument handling for polygon drawing

Specific Objectives

By the end of the lesson, pupils should be able to:

Cognitive Domain:

Define a polygon and state its types.
Explain the square, circle, and diagonal methods of constructing regular polygons.
List reasons for accurate instrument handling in technical drawing.

Affective Domain:

Appreciate the importance of accuracy in technical drawing.
Show interest in constructing various polygons.
Develop patience while using drawing instruments.

Psychomotor Domain:

Construct a regular polygon using the square method.
Construct a regular polygon using the circle method.
Construct a regular polygon using the diagonal method.

Collaborate with peers to share drawing instruments during practical sessions.
Discuss construction steps with classmates.

Reference Materials

The following resources were used in planning this lesson:

9 Years Basic Education Curriculum for Technical Drawing
State Unified Scheme of Work for Senior Secondary Schools
Okoro, P.N. (2010). Technical Drawing for Senior Secondary Schools. Evans Brothers (Nigeria Publishers) Limited.

Instructional Materials

The teacher will teach this lesson with the aid of:

Models of various polygons
Charts showing steps for polygon construction
Posters illustrating regular and irregular polygons
Drawing instruments such as T-square, set squares, compass, protractor, pencils (HB, H, 2H), eraser, and drawing paper.

Rationale for the Lesson

This lesson helps pupils to understand the fundamental geometric shapes that are common in everyday designs and engineering. Learning to construct polygons accurately develops their precision skills, which is important for future technical careers and problem-solving.

Prerequisite/Previous Knowledge

Pupils should have basic knowledge of plane geometric shapes, angles, and the use of fundamental drawing instruments like rulers, pencils, and erasers.

Lesson Content/Board Summary

POLYGONS

Definition of a Polygon

A polygon is a closed plane figure bounded by three or more straight lines (sides). The word “polygon” comes from Greek words meaning “many angles”.

Types of Polygons

Polygons can be classified into two main types:

Regular Polygons: These are polygons where all sides are equal in length, and all interior angles are equal in measure. Examples include equilateral triangle, square, regular pentagon, regular hexagon.
Irregular Polygons: These are polygons where sides and/or interior angles are not all equal.

Methods of Constructing Regular Polygons

Regular polygons can be constructed using various methods depending on the polygon and given information. The common methods include:

1. Square Method of Polygon Construction

This method is suitable for constructing certain regular polygons, particularly those with an even number of sides or derived from a square (e.g., octagon). It involves enclosing the polygon within a square and using its properties to locate vertices.

2. Circle Method of Polygon Construction

This is a general method for constructing any regular polygon. It involves:

Drawing a circumscribing circle for the polygon.
Calculating the central angle (360° divided by the number of sides).
Marking off the central angle repeatedly around the circle to locate the vertices.
Connecting the vertices to form the polygon.

3. Diagonal Method of Polygon Construction

This method involves using the properties of diagonals to construct specific polygons or to locate vertices. For some polygons, the lengths and intersection points of diagonals can be used to accurately draw the shape.

Accurate Instrument Handling for Polygon Drawing

Accurate instrument handling is essential in technical drawing for several reasons:

It ensures precision and neatness in drawings.
It prevents errors and rework.
It produces professional and readable drawings.
It helps in developing good drawing habits.

Teaching Methods/Instructional Techniques

Discussion, Lecture, Demonstration, Question and Answer, Visual Aids

Instructional Procedures

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher greets the pupils and introduces the topic by asking pupils to identify common shapes around them, like the shape of a classroom floor tile (square), a traffic stop sign (octagon), or a football (pentagonal/hexagonal patterns). The teacher then explicitly states that today’s lesson will focus on polygons and their construction.
Pupils’ Activity: Pupils respond to questions and listen attentively.
Learning Point: Pupils are engaged and understand the relevance of polygons in their environment.

Step 2: Definition and Types of Polygons

Time: 7 minutes
Teaching Skill: Explanation/Illustration
Teacher’s Activity: The teacher defines a polygon, explains the difference between regular and irregular polygons, and provides examples using charts and diagrams. The teacher ensures pupils understand these basic concepts.
Pupils’ Activity: Pupils listen, take notes, and ask questions for clarification.
Learning Point: Pupils understand the definition and classification of polygons.

Step 3: Square Method of Polygon Construction

Time: 8 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates the square method of constructing a regular polygon (e.g., an octagon from a square) on the board or using a large drawing sheet. The teacher explains each step clearly, emphasizing the use of drawing instruments.
Pupils’ Activity: Pupils observe the demonstration, noting the steps and instrument usage.
Learning Point: Pupils learn the steps involved in constructing a polygon using the square method.

Step 4: Circle Method of Polygon Construction

Time: 8 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates the circle method for constructing another regular polygon (e.g., a regular hexagon or pentagon) on the board. The teacher guides pupils through calculating the central angle and marking off vertices on the circumference.
Pupils’ Activity: Pupils pay close attention to the demonstration and the calculation of angles.
Learning Point: Pupils understand how to construct a regular polygon using the circle method.

Step 5: Diagonal Method of Polygon Construction

Time: 7 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher explains and demonstrates the diagonal method, perhaps by constructing a specific polygon (e.g., a rhombus or a specific quadrilateral where diagonals are key to its construction) or by showing how diagonals can be used to verify or locate points in a regular polygon. The teacher emphasizes precision.
Pupils’ Activity: Pupils observe and try to grasp the principles of using diagonals in construction.
Learning Point: Pupils learn about the diagonal method and its application in polygon construction.

Step 6: Accurate Instrument Handling

Time: 3 minutes
Teaching Skill: Emphasis/Reinforcement
Teacher’s Activity: The teacher reiterates the importance of accurate instrument handling, demonstrating correct ways to hold pencils, use set squares, and ensure clean lines. The teacher stresses that accuracy leads to correct and neat drawings.
Pupils’ Activity: Pupils listen and note the tips for accurate instrument handling.
Learning Point: Pupils appreciate the value of precision and correct use of drawing instruments.

Step 7: Evaluation/Review

Time: 5 minutes

Teaching Skill: Questioning/Assessment

Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

Define a polygon.
Mention two types of polygons.
State two methods for constructing regular polygons.
Why is accurate instrument handling important in technical drawing?

Pupils’ Activity: Pupils answer orally and in writing.

Learning Point: Pupils demonstrate understanding of the lesson.

Step 8: Conclusion

Time: 2 minutes
Teaching Skill: Summarization/Assignment
Teacher’s Activity: The teacher summarizes the key points of the lesson, emphasizing the different construction methods and the need for accuracy. The teacher assigns homework: pupils are to practice constructing a regular pentagon using the circle method and a regular octagon using the square method.
Pupils’ Activity: Pupils listen to the summary and copy the homework assignment.
Learning Point: Pupils consolidate their learning and are given tasks to reinforce their skills.

Lesson Keywords

Polygon – A closed plane figure bounded by three or more straight lines.
Regular Polygon – A polygon with all sides equal and all angles equal.
Irregular Polygon – A polygon with unequal sides or unequal angles.
Square Method – A construction method involving enclosing a polygon within a square.
Circle Method – A general method using a circumscribing circle and central angles to locate vertices.
Diagonal Method – A construction method that utilizes properties or lengths of diagonals to determine vertices.
Accuracy – The quality of being correct or precise.

Differentiation

For pupils who grasp concepts quickly, the teacher can provide additional challenges, such as constructing a more complex polygon or constructing a polygon with only a given side length. For pupils needing more support, the teacher will provide one-on-one guidance during practical demonstrations and may offer pre-drawn outlines for them to complete the construction steps.

Note for teachers using this lesson plan

Ensure all necessary drawing instruments are available and in good working condition before the lesson. Practical demonstrations are key, so make sure the board or demonstration area is clear and visible to all pupils. Encourage pupils to practice regularly to improve their precision and speed in technical drawing.