PSLE Gabby has a triangular piece of paper RST with SR = ST, ∠RST = 78° and ∠TUU = 70°. RUT and SUT are straight lines. She folded it along the line UV as shown.
- Find ∠w.
- Find ∠x.
(a)
Length of RS = Length of ST
Triangle RST is an isosceles triangle.
∠STR
= (180° - 78°) ÷ 2
= 102° ÷ 2
= 51° (Isosceles triangle)
∠w
= 180° - 70° - 51°
= 59° (Angles sum of triangle)
(b)
∠SRT = ∠STR = 51°
∠y
= 180° - 70° - 70°
= 40° (Angles on a straight line)
∠x
= 180° - 51° - 40°
= 89° (Angles sum of triangle)
Answer(s): (a) 59°; (b) 89°