Mathematics Lab Activity-13 Class IX | Circle

 Lab Activity-13 Class iX

Mathematics Lab Activities on Circle for class IX students, with complete observation tables, strictly according to the CBSE syllabus.

Chapter - 09  circle

Activity - 13

Objective: 

To verify that the opposite angles of a cyclic quadrilateral are supplementary.

Material Required

Chart paper, geometry box, scissors, sketch pens, adhesive, transparent sheet.

Procedure

1. Take a chart paper and draw a circle of any radius on it.

2. In the circle, draw a quadrilateral so that all the four vertices of the quadrilateral lie on the circle. Name the angles and colour them as shown in Fig. 1.

Figure 1

3. Make the cut-outs of the angles as shown in Fig. 2.

Figure 3

4. Paste cut-outs of the opposite angles ∠1 and ∠3, ∠2 and ∠4 to make straight angles as shown in Fig. 3. Thus ∠1 + ∠3 = 180° and ∠2 + ∠4 = 180°.

Figure 3

Observations

On actual measurement:

∠1 = 80°;   ∠3 = 100° ; 

So, ∠1 + ∠3 = 180° 

So, ∠2 + ∠4 =180° ;

∠2 =115° ;  ∠4 = 65°

Result : 

From this activity we find that, sum of each pair of the opposite angles of a cyclic quadrilateral is supplementry.

Applications

The concept may be used in solving various problems in geometry.

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