Page 15 - Module & More Matematik Tambahan Tg5

Matematik Tambahan Tingkatan 5 Bab 1 Sukatan Membulat

9. Tentukan jejari bagi sektor bulatan yang berikut. Beri jawapan kepada dua tempat perpuluhan.
Determine the radius of the following sectors of circles. Give the answers to two decimal places. TP 4

CONTOH (a)
1

BAB 1.6 rad 3.5 rad

Diberi luas sektor ialah 20.5 cm 2 Diberi luas sektor ialah 10.21 cm 2
Given the area of the sector is 20.5 cm 2 Given the area of the sector is 10.21 cm 2
Penyelesaian:
luas sektor q Gunakan /Use
Gunakan = luas sektor q
luas bulatan 2π luas bulatan = 2π
Use area of sector = q area of sector q
area of circle 2π =
20.5 1.6 area of circle 2π
= 10.21 2π – 3.5
πj 2 2π =
πj 2 2π
20.5 × 2
j = 10.21 × 2
2
1.6 j =
2
j = 5.06 cm 2π – 3.5
j = 2.71 cm
(b) (c)
O
38 cm
P
P
O
12 cm
Q Q

2
2
Diberi luas sektor ialah 42 cm dan panjang Diberi luas sektor ialah 85 cm dan panjang
lengkok PQ ialah 12 cm. lengkok PQ ialah 38 cm.
Given that the area of the sector is 42 cm and the Given that the area of the sector is 85 cm and the arc
2
2
arc length of PQ is 12 cm. length of PQ is 38 cm.
Gunakan/Use Gunakan/Use
panjang lengkok = luas sektor 38 = πj – 85
2
2πj luas bulatan 2πj πj 2
arc length area of sector 2(πj – 85)
2
2πj = area of circle j = 38
12 42 2
= 2(πj – 85) = 38j
2πj πj 2 πj – 19j – 85 = 0
2
42 × 2 19 ± (–19) – 4π(–85)
2
j = j =
12 2π
= 7 cm j = 9.04 cm

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