PSLE Jane has a triangular piece of paper GHJ with HG = HJ, ∠GHJ = 78° and ∠JKK = 70°. GKJ and HKJ are straight lines. She folded it along the line KL as shown.
- Find ∠m.
- Find ∠n.
(a)
Length of GH = Length of HJ
Triangle GHJ is an isosceles triangle.
∠HJG
= (180° - 78°) ÷ 2
= 102° ÷ 2
= 51° (Isosceles triangle)
∠m
= 180° - 70° - 51°
= 59° (Angles sum of triangle)
(b)
∠HGJ = ∠HJG = 51°
∠p
= 180° - 70° - 70°
= 40° (Angles on a straight line)
∠n
= 180° - 51° - 40°
= 89° (Angles sum of triangle)
Answer(s): (a) 59°; (b) 89°