The figure, not drawn to scale, O is the centre of the circle and BG // CF // DE. Find
- ∠AOD
- ∠AFO
(a)
∠GOC
= 180° - 100°
= 80° (Interior angles, BG//CO)
∠ODF = ∠OFD = 30° (Isosceles triangle)
∠COD
= 30° + 30°
= 60° (Exterior angle of a triangle)
∠AOD
= 80° + 60°
= 140°
(b)
∠FOD
= 180° - 30° -30°
= 120° (Isosceles triangle)
∠AOF
= 360° - 140° - 120°
= 100° (Angles at a point)
AO = OF = Radius
∠AFO
= (180° - 100°) ÷ 2
= 80° ÷ 2
= 40° (Isosceles triangle)
Answer(s): (a) 140°; (b) 40°