Page 50 - Mathematics Class - IX
P. 50
ACTIVITY 4.3
OBJECTIVE
To verify experimentally that in a triangle, the longer side has the greater angle opposite to it.
MATERIALS REQUIRED
Cardboard Scissors
Coloured glazed papers Geometry box
White paper Sketch pens
Tracing paper Adhesive
PRE-REQUISITE KNOWLEDGE
Concept of properties of a triangle.
THEORY
We know that the sum of angles in a triangle is equal to 180°.
PROCEDURE
1. Take a cardboard of suitable size and paste a white paper on it.
2. Cut out a ∆ABC from a glazed paper and paste it on the cardboard as shown in Fig. (a).
3. Measure the lengths of all the three sides of ∆ABC and identify that which of them is longest.
4. Mark the three angles of a triangle Fig. (b).
5. Using a tracing paper, mark the cut out of the angle opposite to the longest side BC, i.e. ∠A Fig. (c).
A A
B C B C
Fig. (a) Fig. (b)
A
Fig. (c)
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