PSLE Opal has a triangular piece of paper STU with TS = TU, ∠STU = 78° and ∠UVV = 72°. SVU and TVU are straight lines. She folded it along the line VW as shown.
- Find ∠x.
- Find ∠y.
(a)
Length of ST = Length of TU
Triangle STU is an isosceles triangle.
∠TUS
= (180° - 78°) ÷ 2
= 102° ÷ 2
= 51° (Isosceles triangle)
∠x
= 180° - 72° - 51°
= 57° (Angles sum of triangle)
(b)
∠TSU = ∠TUS = 51°
∠z
= 180° - 72° - 72°
= 36° (Angles on a straight line)
∠y
= 180° - 51° - 36°
= 93° (Angles sum of triangle)
Answer(s): (a) 57°; (b) 93°