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To find the area of the D OPQ. Draw QM ^ OP.
Since Ð POQ = 300 we have QM = 1/2 (OQ) = 3 cms.
Area of the D OPQ = 1/2 OP. QM = 1/2 x 6 x 3 = 9 sq. cm.

Area of the shaded portion = area of sector - area of triangle

  = (3p - 9) sq. cm

= 3 (p - 3) sq. cm

» 3(3.14 - 3) sq. cm

» 0.42 sq. cm

(6) Two circles each of radius 5 cms intersect each other. If the distance between their centre is 5 Ö2 cms. Find the area common to the circles.

Solution

From the fig. It is clear that PQ2 = PA2 + QA2

Since (5 Ö2 )2 = (5)2 + (5)2 i.e 50 = 25 + 25
\ By the converse of Pythagoras theorem,


D PAQ is a right D with Ð A = 900 and Ð APQ = 450

\ Ð APB = 900 Let APB = q = 900 = p/2 rad

Now area of sector P - AB = 1/2 r 2 qc = (5)2 p/2
= 25/4 p sq.cms



Also Area of square APBQ = (side) 2 = (5) 2 = 25 sq. cms.

 

[next page]

 

Index

1.1 Angles (Radians & Degrees)
1.2 Arc Length & Area of the circle
Supplementary Problems

Chapter 2





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