Class 07 ACTIVITY 4 - TRIANGLES

 ACTIVITY 4 - TRIANGLES

Objective: 

To medians get the pass medians through of a a common triangle by point paper. folding. Also, to verify that in a triangle medians pass through a common point.

Materials Required: 

Tracing paper, colour pencils, geometry box, etc.

Procedure:

1. On a. tracing paper, trace the following triangles. Cut out each triangle from the tracing paper. Note that triangle (a) is an equilateral triangle, triangle (b) is isosceles as well as right angled triangle and  triangle(c) is as a scalene triangle. We can also say that triangle (a) is an acute angled triangle, (b) is right angled triangle, (c) is an obtuse angled triangle.

2. Fold each triangular cut out such that the vertex Q coincides with the vertex R.

3. Unfold each tracing paper. In each case mark the point of intersection of QR and the crease as X. Draw PX as dotted line.

4. Now, fold each triangular cut out such that the vertex P and R coincide.

5. Unfold each tracing paper. In each case mark the point of intersection of PR and the crease P as Y. Draw QY as a dotted line.

6. Finally fold each triangular cutout such that the vertex P coincides with the vertex Q.

7. Unfold each tracing paper. In each case mark the point of intersection of PQ and the crease as Z. Draw RZ as a dotted line. 

Observations :

In figure 3, X is the mid point of QR. So PX is a median of  each triangle.

2. Similarly in figures 5 and 7,  Y and Z are mid points PR and PQ respectively. So QY and RZ are medians of ∆PQR in each case.

3. Also  in figure 7, we see that in each case all the three medians pass through a common point O.

Conclusion

A triangle has three medians.

2. All the three medians of a triangle pass through a common point. This point is called the centroid of the angle.

Do Yourself: 

Draw an acute angled, a right angled and an obtuse angled triangle. By paper folding, verify that in each case the three medians are  concurrent.