Skip to main content

Session 37: Triangles

Session Title

Triangle

Objective

By the end of the lesson, students will be able to:


  1.  Identify and name triangles based on sides and angles.
  2.  Understand that a triangle has 3 sides and 3 angles.
  3.  Discover and state that the sum of the interior angles of a triangle is 180°.
  4.  Collaborate in groups and reflect on their learning.

Concept

The world of triangles

Materials Required
  1. Pictures of triangle, square, rectangle, circle
  2. Instruments box
  3. Board & Chalk
  4. A4 sheet & Crayons 
  5. Work sheet

Methodology

Activity oriented

Session Duration

 90 Minutes

 

Introduction Activity (15 minutes): 

Mandala Patterns 

  • Concepts: Circles, radial symmetry, angles, pattern repetition

How:

  • Students use compasses and protractors to make mandalas.
  • Emphasizes symmetry and repeated geometric patterns.
  • Can be colored for relaxing mindfulness activity too.

Example: (Draw the picture given below on a chart)

AD_4nXcpdbY2wJN1ijd1UqkzYT_RxATUSTuPalAvm6TOp9C1HrKBDeZJiN9E3aQ8lqiTgsYQRjKQAt9CCafamVfSdyFCpY0-gg_oTFGYyGG_oFrHLrIzEjpLPEKYrbibnIcwhd33p5IPKg?key=cRT8aGN5drCWLEYfTuvgiYl3

Main Activity (65 minutes):

What’s a Triangle?  Discussion (10 minutes):

    Show pictures of different shapes (triangle, square, rectangle, circle).

    Ask: Which one is a triangle? How do you know?

    Students share prior knowledge.

    Teacher highlights: 

    A triangle has 3 sides and 3 angles. It’s a closed shape.

    Story Time (15 minutes):

    In the Triangle Kingdom, every triangle has a secret code: its 3 angles must always work together to form a straight line (180°) to keep the kingdom safe!

    Characters:-

    •  Prince Equi (Equilateral)
    •  Sir Righty (Right triangle)
    •  Lady Acuta (Acute triangle)
    •  General Obtusa (Obtuse triangle)

    The sum of the interior angles of any triangle is always equal to 180 degrees.

    In mathematical notation, for a triangle ABC with interior angles angle A, angle B, and angle C, the triangle sum theorem can be expressed as:

    ‹A + ‹ B + ‹C = 180⁰

    Ask: Can you guess how their angles work together?  

    Student Engagement (10 minutes):

    Ask students to act out triangle characters (e.g., stretch arms to represent different angles).

    Key Concept (10 minutes):

    Definition of a triangle

    • A closed figure with 3 sides and 3 angles.

    Types of triangles by sides

    • Equilateral (3 equal sides)
    • Isosceles (2 equal sides)
    • Scalene (no equal sides)

    Types of triangles by angles

    • Acute triangle (all angles < 90°)
    • Right triangle (one angle = 90°)
    • Obtuse triangle (one angle > 90°)

    Group Activity- Angle Detectives (20 minutes):

    Make students into small groups(3 or 4)

    AD_4nXc60s4aku5Ew7qXv-Z0GfAXo_4iJE0XK7WZQa7kvLDaqRd1CAJvFmOYCA2_EgHRvYJdrbPemHM5HHIoGTXVgkNhQe0o7idAvr8qwODOWFNp2uu9Tbcm5C6PgI58M0x0HGKtItAO?key=cRT8aGN5drCWLEYfTuvgiYl3

    • Give each group a work sheet of  triangle with one missing angle.
    • Students solve for the missing angle by subtracting from 180°.

    Review Questions (5 minutes):

    1. What is a triangle?
    2. How many angles does a triangle have?

    Follow up Task (5 minutes):

    1. Name a real-life object or structure that uses a triangle shape. Why is it used?
    2. Draw a triangle where one angle is 90°. What type of triangle is it?

    Expected Learning Outcome:

    Knowledge building:

    • This focuses on conceptual understanding and facts. You help students understand what a triangle is, its types, and properties.

    Skill building:

    • Conceptual understanding
    • Problem solving

    Resources:

    Missing triangles:

    https://drive.google.com/file/d/1lkchm4tNLyq2JxJMW7rv2Si1XgdzZI7h/view?usp=drivesdktriangles




    Back to top