PSLE Irene has a triangular piece of paper DEF with ED = EF, ∠DEF = 84° and ∠FGG = 69°. DGF and EGF are straight lines. She folded it along the line GH as shown.
- Find ∠j.
- Find ∠k.
(a)
Length of DE = Length of EF
Triangle DEF is an isosceles triangle.
∠EFD
= (180° - 84°) ÷ 2
= 96° ÷ 2
= 48° (Isosceles triangle)
∠j
= 180° - 69° - 48°
= 63° (Angles sum of triangle)
(b)
∠EDF = ∠EFD = 48°
∠l
= 180° - 69° - 69°
= 42° (Angles on a straight line)
∠k
= 180° - 48° - 42°
= 90° (Angles sum of triangle)
Answer(s): (a) 63°; (b) 90°