ABCD is a quadrilateral and OADC is a trapezium in which OA // DC and ∠BAD = 109°, ∠ADC = 120°, ∠BCD = 62° and DC = DA. Find
- ∠ABO
- ∠DAO
- ∠ACD.
(a)
∠ABO
= 360° - 120° -109° - 62°
= 69° (Sum of angles in a quadrilateral)
(b)
∠DAO
= 180° - 120°
= 60° (Interior angles, AO//DC)
(c)
∠ACD
= (180° - 120°) ÷ 2
= 60 ÷ 2
= 30° (Isosceles triangle)
Answer(s): (a) 69°; (b) 60°; (c) 30°