Class: Junior Secondary School 2 (JSS2, JSS 2)
Term: 2nd Term
Week: 7
Age: 13 years
Duration: 45 minutes
Subject: Mathematics
Curriculum Theme: Mathematics
Previous Lesson: Properties of Parallelogram, Rhombus and Kite
Topic: Angles In Polygons
Subject Matter: Revision of angles in a triangle, Identification and naming of polygons (up to 10 sides), Sum of angles in a quadrilateral, The sum of interior angles in a polygon using (n−2)180° or (2n−4)90°

Specific Objectives

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

Cognitive Domain:
(a) Recall facts on angles in triangles and quadrilaterals.
(b) Identify and name polygons up to 10 sides.
(c) Calculate the sum of interior angles of polygons using (n−2)180° or (2n−4)90°.
Affective Domain:
(a) Show interest and confidence in solving polygon-related angle problems.
Psychomotor Domain:
(a) Draw and label given polygons with correct number of sides.
Social Domain:
(a) Work cooperatively in groups to solve angle problems involving polygons.

Reference Materials

The following resources was used in planning this lesson:

9 Years Basic Education Curriculum
Lagos State Unified Scheme of Work for Junior Secondary Schools
Wikipedia – Polygon
Relevant Textbooks

Instructional Materials

The teacher will teach this lesson with the aid of:

Charts of different polygons
Protractor, ruler, and pencils
Flash cards showing polygon names and sides
Whiteboard and marker
A model triangle and quadrilateral

Rationale for the Lesson

This lesson deepens learners’ understanding of angle relationships in polygons and strengthens their ability to identify, classify, and calculate interior angle sums in geometric shapes.

Prerequisite/Previous Knowledge

Pupils already know how to measure angles, classify triangles, and identify basic shapes from previous classes.

Lesson Content/Board Summary

Lesson Content

Angles in Polygons

Revision of Angles in a Triangle

A triangle is a three-sided polygon whose interior angle sum is always 180°.
These include:

Sum of all interior angles = 180°.
Each angle in an equilateral triangle = 60°.
A right-angled triangle has one 90° angle.

Identification and Naming of Polygons

A polygon is a closed shape made of straight lines. Polygons are named according to the number of their sides.
Examples include:

Triangle – 3 sides
Quadrilateral – 4 sides
Pentagon – 5 sides
Hexagon – 6 sides
Heptagon – 7 sides
Octagon – 8 sides
Nonagon – 9 sides
Decagon – 10 sides

Sum of Angles in a Quadrilateral

A quadrilateral has four sides. It can be divided into two triangles, and the sum of its interior angles is always 360°.
The following are:

Interior angle sum = 360°.
Examples include: square, rectangle, rhombus, and kite.

Sum of Interior Angles in a Polygon

The interior angle sum of any polygon depends on the number of sides. It can be found using two formulas:

(n−2)180°
(2n−4)90°

Examples are:

For a pentagon (n=5):
Sum = (5−2)180° = 3 × 180° = 540°.
For an octagon (n=8):
Sum = (8−2)180° = 6 × 180° = 1080°.
For a decagon (n=10):
Sum = (10−2)180° = 8 × 180° = 1440°.

Teaching Methods/Instructional Techniques:

Discussion, Lecture, Explanation, Demonstration, Group Work, Question and Answer, Visualization

Instructional Procedures

To deliver this lesson, the teacher will adopt the following steps:

Step 1: Introduction

Time: 5 minutes
Teaching Skill: Set Induction
Teacher’s Activity: The teacher displays drawings of common shapes and asks pupils to recall the angle sum of a triangle and quadrilateral.
Pupils’ Activity: Pupils respond and share what they remember.
Learning Point: Pupils link previous knowledge to the new lesson.

Step 2: Revision of Angles in Triangle and Quadrilateral

Time: 7 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher explains the known angle sums in triangles and quadrilaterals using board sketches.
Pupils’ Activity: Pupils observe, listen, and answer brief questions.
Learning Point: Pupils reinforce foundational geometric facts.

Step 3: Identification and Naming of Polygons

Time: 10 minutes
Teaching Skill: Discussion
Teacher’s Activity: The teacher presents polygon charts and guides pupils to identify and name polygons up to 10 sides.
Pupils’ Activity: Pupils name the polygons and count their sides.
Learning Point: Pupils understand how polygons are classified.

Step 4: Calculating Sum of Interior Angles in Polygons

Time: 13 minutes
Teaching Skill: Demonstration
Teacher’s Activity: The teacher demonstrates the use of (n−2)180° to calculate interior angle sums and solves examples on the board.
Pupils’ Activity: Pupils attempt similar problems individually or in groups.
Learning Point: Pupils learn to apply formulas to solve polygon angle problems.

Step 5: Note-Taking

Time: 5 minutes
Teaching Skill: Explanation
Teacher’s Activity: The teacher writes the board summary for pupils to copy.
Pupils’ Activity: Pupils copy the notes.
Learning Point: Pupils keep accurate study notes.

Step 6: Evaluation/Review

Time: 3 minutes
Teaching Skill: Questioning
Teacher’s Activity: The teacher evaluates the learning by asking the following questions:

State the sum of angles in a quadrilateral.
Name any four polygons and their number of sides.
Find the sum of interior angles in a hexagon.
Calculate the interior angle sum of an octagon.
Pupils’ Activity: Pupils answer orally.
Learning Point: Pupils show mastery of the lesson.

Step 7: Conclusion

Time: 2 minutes
Teaching Skill: Reinforcement
Teacher’s Activity: The teacher summarizes the main ideas and encourages constant practice of angle calculations.
Pupils’ Activity: Pupils listen and ask questions.
Learning Point: Pupils retain key points of the lesson.

Lesson Keywords

Polygon – a closed shape made of straight lines
Interior Angle – an angle inside a polygon
Quadrilateral – a polygon with four sides
Formula – a rule for calculating values
Decagon – a polygon with ten sides

Differentiation

Provide simpler shapes and fewer-step problems for slower learners, while advanced pupils solve polygons with higher sides and apply both formulas.

Note for teachers using this lesson plan

Use clear diagrams, ensure accuracy in drawings, and guide pupils patiently when applying formulas. Encourage peer support during group problem-solving.