Answer:
(a) 5.4 rad
(b) 6 : 5
(c) 27.52 cm
Explanation:
(a)
Given:
length OB = 2OC
Ratio of AB : CD = 3 : 5
∠AOB = 1/2 x 3/5 x 1.8 = 0.54 rad
(b)
Area of COD = 1/2(r)² (1.8) = 0.9r²
Area of AOB = 1/2 (2r)²(0.54) = 1.08r²
Ratio of AOB : COD
= 1.08r² : 0.9r²
= 1.08 : 0.9
= 6 : 5
(c)
Given :
CD = 7.2cm
Ratio of AB : CD = 3 : 5
(1.8)r = 7.2
r = 4
AB = 3/5 x 7.2 = 4.32
Perimeter
= 7.2 + 4.32 + 4 + 4 + 2x4
= 27.52 cm