1、y=tanθ 在[30°,90°)递增,在(90°,120°]递增
故 tanθ ≥tan30° = √3 /3 或 tanθ ≤ tan120° = -√3
即 tanθ∈(-∞,-√3)∪[√3 /3,+∞)
2、y=sinθ在[-2π/3,-π/2]递减,在[-π/2,π/6]递增
sin(-2π/3) = -√3 /2
sin(-π /2) = -1
sin(π/6) = 1/2
∴sinθ∈[-1,1/2]