PSLECDEF is a parallelogram, CEG is an equilateral triangle and EF = FG.
- Find ∠CEF.
- Find ∠EFC.
- Find ∠GCD.
(a)
EF = FG
Triangle EFG is an isosceles triangle.
∠FEG
= (180° - 140°) ÷ 2
= 40° ÷ 2
= 20° (Isosceles triangle)
∠CEF
= 60° - 20°
= 40° (Equilateral triangle)
(b)
∠CGF
= 60° - 20°
= 40° (Equilateral triangle)
∠CFG
= 180° - 40° - 20°
= 120° (Angles sum of triangle)
∠CFE
= 360° - 140° - 120°
= 100° (Angles at a point)
∠DCE
= ∠CEF
= 40° (Alternate angles)
∠DCG
= 60° + 40°
= 100°
Answer(s): (a) 40°; (b) 100°; (c) 100°
