PSLE Olivia has a triangular piece of paper ABC with BA = BC, ∠ABC = 80° and ∠CDD = 70°. ADC and BDC are straight lines. She folded it along the line DE as shown.
- Find ∠f.
- Find ∠g.
(a)
Length of AB = Length of BC
Triangle ABC is an isosceles triangle.
∠BCA
= (180° - 80°) ÷ 2
= 100° ÷ 2
= 50° (Isosceles triangle)
∠f
= 180° - 70° - 50°
= 60° (Angles sum of triangle)
(b)
∠BAC = ∠BCA = 50°
∠h
= 180° - 70° - 70°
= 40° (Angles on a straight line)
∠g
= 180° - 50° - 40°
= 90° (Angles sum of triangle)
Answer(s): (a) 60°; (b) 90°