(2)
In figure 7.29, P is the centre of the
circle of radius 6 cm. Seg QR
is a tangent at Q. If PR = 12,
find the area of the shaded region.
(V3 = 1.73)
Fig. 7.29
Answers
Explanation:
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Explanation:
Since line drawn from the centre of a circle to the tangent is perpendicular to the tangent.
∴OQ perpendicular to QR
△OQR is a right angled triangle.
∴OR
2
=QR
2
+OQ
2
⇒QR=
OR
2
−OQ
2
=
20
2
−10
2
=
400−100
=
300
=10
3
∴ Area of △ OQR=
2
1
×QR×OQ
=
2
1
×10
3
×10
=86.5cm
2
Also,let ∠QOR=θ
sinθ=
OR
QR
=
20
10
3
θ=60
o
∴ Area of sector OQT=π(10)
2
×
360
60
=
7
22
×100×
360
60
=52.33cm
2
Area of the shaded region = Area of △ OQR - Area of sector OQT
= (86.5−52.33)cm
2
= 34.17cm
2