Lets verify that the sum of the angles of a triangle is 180^{o}.

## Materials Required

1. Hardboard sheet

2. Glazed papers

3. Sketch pens/pencils

4. Scissors

5. Tracing paper

6. Adhesive

7. Drawing sheet

8. Geometry box.

### Procedure

1. Take a hardboard sheet of a convenient size and paste a white paper on it.

2. Cut out a triangle from a drawing sheet, and paste it on the hardboard and name it as ΔABC.

3. 3. Mark its three angles.

4. Cut out the angles respectively equal to ∠A, ∠B and ∠C from a drawing sheet using tracing paper.

5. Draw a line on the hardboard and arrange the cut-outs of three angles at a point O. See the reference image below.

### Demonstration

The three cut-outs of the three angles A, B and C placed adjacent to each other at a point form a line forming a straight angle = 180^{o}. It shows that sum of the three angles of a triangle is 180^{o}. Therefore, ∠A + ∠B + ∠C = 180^{o}.

### Observation

Measure of ∠A = ....................

Measure of ∠A = ....................

Measure of ∠A = ....................

Sum (∠A + ∠B + ∠C) = ............

### Result

Thus, the sum of the three angles of a triangle is 180^{o}

### Application

This result may be used in a number of geometrical problems such as to find the sum of the angles of a quadrilateral, pentagon, etc.