nomor 18 dan nomor 19 yaa

#18
n = keliling total

40/360 x n = 12,56
1/9 x n = 12,56
n = 12,56 x 9
n = 113,04

K = 22/7 x diameter
113,04 = 3,14 x d
d = 113,04 / 3,14
d = 36

L = 3,14 x 18 x 18
L = 1017,36

L AOB:
= 1/9 x 1017,36
= 113,04 cm²

#19
Jari jari busur besar:
= 18 + 6
= 24

Jari-jari busur kecil:
= 18

Panjang CD:
= 30/360 x 3,14 x 24
= 1/12 x 75,36 cm
= 6,28 cm

Panjang AB:
= 1/12 x 3,14 x 18
= 4,71 cm

Keliling yang diarsir:
= 6,28 + 4,71 + 12
= 22,99 cm

Jadikan terbaik ya, makasih