how to make exterior angle property – theorem working model – maths tlm

In this post we write about making of the exterior angle property – theorem working model – maths tlm – triangle using cardboard in simple and easy manner

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Creating a working model to demonstrate the exterior angle property of a triangle using cardboard and syringes is a great hands-on project.

The exterior angle property states that the measure of an exterior angle of a triangle is equal to the sum of the measures of the two non-adjacent interior angles.

Here’s how you can create this model:

Materials Needed:

  • Cardboard (for triangles and base)
  • Syringes (without needles)
  • Plastic tubing (to connect syringes)
  • Ruler
  • Scissors or craft knife
  • Glue or hot glue gun
  • Protractor (for accurate angle measurement)
  • Marker or pen
  • Color paper (optional, for decoration)
  • Tape

Step by Step Video Making on exterior angle property – theorem working model – maths tlm

1. Prepare the Triangles and Base

  1. Base Preparation:
    • Cut a large rectangular piece of cardboard to serve as the base of your model. This will hold the triangles and syringes.
  2. Triangle Construction:
    • Cut out three identical triangles from the cardboard. Make sure they are all equilateral triangles for simplicity.
    • Label the vertices of each triangle as A, B, and C.

2. Create the Exterior Angle Mechanism

  1. Create the Exterior Angle:
    • Extend one side of each triangle to form an exterior angle. For example, extend side BC to form the exterior angle at vertex A.
    • Cut a small piece of cardboard to represent the exterior angle and attach it to the extended side of the triangle using a hinge made from tape. This piece should be able to move.
  2. Attach Syringes:
    • Attach one syringe to each triangle at vertex A where the exterior angle is formed.
    • Attach another syringe to the cardboard base. These syringes will be used to move the triangles to demonstrate the property.
  3. Connect Syringes with Tubing:
    • Connect the syringes using plastic tubing. Make sure the tubing is securely attached to the syringes.
    • When you push the plunger of one syringe, it should move the corresponding triangle, demonstrating the exterior angle property.

3. Assemble the Model

  1. Fix the Triangles on the Base:
    • Attach the triangles to the cardboard base using glue or tape. Ensure that the syringes are properly aligned and can move the triangles without obstruction.
  2. Mark the Angles:
    • Use a protractor to measure and mark the angles on each triangle.
    • Label the interior angles (∠A, ∠B, ∠C) and the exterior angle (∠A’).

4. Demonstrate the Exterior Angle Property

  1. Push the Syringe:
    • Push the plunger of the syringe attached to the triangle. This will move the triangle and the exterior angle.
    • Observe how the movement of the syringe affects the exterior angle.
  2. Show the Property:
    • Demonstrate that the measure of the exterior angle (∠A’) is equal to the sum of the measures of the two non-adjacent interior angles (∠B + ∠C).

By following these steps, you can create an effective and interactive working model that demonstrates the exterior angle property of triangles.

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