Class 09 To verify experimentally that in a triangle, the longer side has the greater angle opposite to it.

 

Activity 18

 OBJECTIVE                                                                    

To verify experimentally that in a triangle, the longer side has the greater angle opposite to it.

MATERIAL REQUIRED

 Coloured paper, scissors, tracing paper, geometry box, cardboard sheet, sketch pens.

 METHOD OF CONSTRUCTION

 1.    Take a piece of cardboard of a convenient size and paste a white paper on it.

 2.   Cut out a ΔABC from a coloured paper and paste it on the cardboard [see Fig. 1].

 3.   Measure the lengths of the sides of ΔABC.

 4.   Colour all the angles of the triangle ABC as shown in Fig. 2.

 5.   Make the cut-out of the angle opposite to the longest side using a tracing paper [see Fig. 3].

DEMONSTRATION

 Take the cut-out angle and compare it with other two angles as shown in Fig. 4.

 ∠A is greater than both ∠B and ∠C.

 i.e., the angle opposite the longer side is greater than the angle opposite the other side.

 OBSERVATION

 Length of side AB = .......................

 Length of side BC = .......................

 Length of side CA = .......................

 Measure of the angle opposite to longest side = .......................

 Measure of the other two angles = ...................... and .......................

 The angle opposite the ...................... side is ...................... than either of the other

 two angles.

 APPLICATION

 The result may be used in solving different geometrical problems.