PSLE BCDE and CEFG are rhombuses. DHE is a straight line.
- Find ∠ECH.
- Find ∠DEF.
(a)
∠CED
= (180° - 100°) ÷2
= 80° ÷ 2
= 40° (Isosceles triangle)
∠ECH
= 180° - 120° - 40°
= 20° (Angles sum of triangle)
(b)
∠CGF
= 360° - 289°
= 71° (Angles at a point)
∠CEF = ∠CGF = 71° (Rhombus)
∠DEF
= 71° - 40°
= 31°
Answer(s): (a) 20°; (b) 31°