PSLEJKLM is a parallelogram, JLN is an equilateral triangle and LM = MN.
- Find ∠JLM.
- Find ∠LMJ.
- Find ∠NJK.
(a)
LM = MN
Triangle LMN is an isosceles triangle.
∠MLN
= (180° - 140°) ÷ 2
= 40° ÷ 2
= 20° (Isosceles triangle)
∠JLM
= 60° - 20°
= 40° (Equilateral triangle)
(b)
∠JNM
= 60° - 20°
= 40° (Equilateral triangle)
∠JMN
= 180° - 40° - 20°
= 120° (Angles sum of triangle)
∠JML
= 360° - 140° - 120°
= 100° (Angles at a point)
∠KJL
= ∠JLM
= 40° (Alternate angles)
∠KJN
= 60° + 40°
= 100°
Answer(s): (a) 40°; (b) 100°; (c) 100°