ACTIVITY - Triangles
Objective:
To verify that the sum of all interior angles of a triangle is 180 °, by papercutting and pasting.
Materials Required:
White sheets of paper, colour pencils, a pair of scissors, geometry box, etc.
Procedure:
On a white sheet of paper, draw a triangle ABC. Using colour pencils mark its angles as shown.
2. Using a pair of scissors, cut out the three angular regions.
3. Draw a line segment XY and mark a point on it.
4. Paste the three angular cut outs so that the vertex of each falls at O as shown in the figure.
Observations:
In figure 4, we see that the angular cutouts neither overlap nor leave any gap between them. But, XOY is a straight angle So, ∠A + ∠ B + ∠C = 180 ° Or sum of the angles of a triangle is 180 °.
Conclusion:
From the above activity, it is verified that the sum of all interior angles of a triangle is 180 °
Do Yourself:
Draw an acute angled triangle, a right triangle and an obtuse angled triangle. By paper cutting and pasting, verify the above property for each triangle.
