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

**Base Preparation**:- Cut a large rectangular piece of cardboard to serve as the base of your model. This will hold the triangles and syringes.

**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

**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.

**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.

**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

**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.

**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

**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.

**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.