Mathematics - Junior Secondary 3 - Construction of angles

Construction of angles

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TERM: 3RD TERM

WEEK 1

Class: Junior Secondary School 3
Age: 14 years
Duration: 40 minutes of 5 periods
Subject: Mathematics
Topic: Construction of Angles
Focus: Construction of Angle 45° and Angle 30°
SPECIFIC OBJECTIVES:
By the end of the lesson, pupils should be able to:

  1. Construct an angle of 45°.
  2. Construct an angle of 30°.
  3. Use a protractor and ruler to accurately construct angles.
  4. Identify and name the parts of the constructed angle (vertex, arms, and angle measure).
  5. Apply angle construction in solving geometric problems.

INSTRUCTIONAL TECHNIQUES:
• Question and answer
• Guided demonstration
• Practical construction
• Problem-solving exercises

INSTRUCTIONAL MATERIALS:
• Protractors
• Rulers
• Set squares
• Worksheets
• Whiteboard and marker

 

PERIOD 1 & 2: Construction of Angle 45°

PRESENTATION:

Step

Teacher’s Activity

Pupil’s Activity

Step 1 - Introduction

Explains the concept of angle construction and its uses.

Pupils listen and ask questions.

Step 2 - Explanation

Demonstrates the construction of a 45° angle using a protractor and ruler.

Pupils observe the teacher’s demonstration.

Step 3 - Demonstration

Draws a straight line, marks a point, and shows how to use the protractor to measure 45°.

Pupils practice drawing lines and using the protractor to mark angles.

Step 4 - Practice

Pupils construct a 45° angle with their protractors.

Pupils construct a 45° angle on their own using rulers and protractors.

NOTE ON BOARD:
• Step 1: Draw a straight line.
• Step 2: Place the protractor at the vertex of the line.
• Step 3: Measure 45° from the baseline.
• Step 4: Draw the second arm of the angle.

EVALUATION (5 exercises):

  1. Construct a 45° angle using the steps provided.
  2. Write down the parts of an angle.
  3. How do you ensure your angle is accurate?
  4. If you are constructing a 45° angle, what should the angle on the opposite side be?
  5. Construct an angle of 45° and check if the arms are equal.

CLASSWORK (5 questions):

  1. Construct a 45° angle using a protractor.
  2. Draw a line and label the vertex and arms of your 45° angle.
  3. Calculate the sum of the angles formed by the 45° angle and its adjacent angle.
  4. Draw two intersecting lines and measure the angles.
  5. Compare your angle with a classmate’s and check if they match.

ASSIGNMENT (5 tasks):

  1. Construct a 45° angle and measure it.
  2. Describe the method used to construct a 45° angle.
  3. Solve for the missing angle if one of the adjacent angles measures 135°.
  4. Write down three real-life applications where constructing angles is used.
  5. Practice constructing a 45° angle without using a protractor.

 

PERIOD 3 & 4: Construction of Angle 30°

PRESENTATION:

Step

Teacher’s Activity

Pupil’s Activity

Step 1 - Introduction

Recaps the construction of the 45° angle. Introduces the construction of a 30° angle.

Pupils recall how to construct angles and ask questions.

Step 2 - Explanation

Demonstrates how to construct a 30° angle with a protractor.

Pupils observe the teacher’s demonstration.

Step 3 - Demonstration

Draws a straight line, marks the vertex, and uses the protractor to measure 30°.

Pupils follow along and attempt the construction themselves.

Step 4 - Practice

Pupils work on constructing a 30° angle independently.

Pupils practice constructing a 30° angle.

NOTE ON BOARD:
• Step 1: Draw a baseline.
• Step 2: Place the protractor at the vertex.
• Step 3: Mark 30° on the protractor and draw the second arm.
• Step 4: Label the vertex and the two arms of the angle.

EVALUATION (5 exercises):

  1. Construct a 30° angle using the steps provided.
  2. What is the difference between a 30° and 45° angle?
  3. How do you check if your angle is accurate?
  4. If two 30° angles are adjacent, what is the total angle between them?
  5. Compare the 30° angle with the 45° angle. Which one is larger?

CLASSWORK (5 questions):

  1. Construct a 30° angle using a protractor.
  2. Label the parts of the 30° angle.
  3. If the two arms of the 30° angle were extended, what other angle would be formed?
  4. Draw two 30° angles and calculate their sum.
  5. How would you adjust the protractor if the angle you are constructing is 30° instead of 45°?

ASSIGNMENT (5 tasks):

  1. Construct a 30° angle and measure it.
  2. Identify the adjacent angle to a 30° angle.
  3. Draw a triangle with one angle of 30° and measure the other two angles.
  4. Describe the method used to construct a 30° angle.

Practice constructing a 30° angle without using a protractor.