2. the diagram shows a sector OAB of a circle with centre O and radius 5cm. the angle between the radii OA and OB is θ radians. the length of the arc AB is 4cm
a) find the value of θ
b) find the area of the sector OAB
No diagram shown....but we can still figure it out
(a)
r = 5 AB = 4
arc length = r*θ
So
4 = 5*θ ⇒ θ = 4/5 (rads)
(b)
Area of a sector = (1/2) r^2 θ = (1/2) (5)^2 (4/5) = [ 25 * 4 ] / 10 = 100 / 10 = 10 cm^2
+-40 
