Understanding the Triangle Sum Theorem
To demonstrate that the sum of the three angles in a triangle is always 180 degrees, we can follow a simple and engaging activity.
Materials Needed
- A piece of paper
- A ruler
- A protractor
- Scissors
Activity Steps
1. Draw a Triangle
- Use the ruler to draw a triangle of any size on the paper. Label the corners as A, B, and C.
2. Measure the Angles
- Using the protractor, measure each angle at points A, B, and C. Record these measurements.
3. Cut Out the Triangle
- Carefully cut out the triangle along the edges.
4. Arrange the Angles
- Cut off each angle at points A, B, and C. You now have three angle pieces.
5. Form a Straight Line
- Arrange the three angles on a flat surface so that the angles meet at a single point, creating a straight line.
Observation
- You will notice that when the angles are arranged, they form a straight line. According to geometry, the total measure of a straight angle is 180 degrees.
Conclusion
- Therefore, by measuring the angles and arranging them, it is visually evident that the sum of the angles A, B, and C is 180 degrees. This activity not only proves the Triangle Sum Theorem but also enhances understanding through a hands-on approach.
By engaging in this activity, one can easily grasp the fundamental property of triangles, reinforcing the concept in a fun and interactive manner.

the sum of three angles is 180 degree if they are on same side of transversal or if they are on a straight line.