已知向量OA=（λcosa,λsina)(λ≠0）向量OB=(-sinβ,cosβ),其中O为坐标原点

let x = OA与OB的夹角
|OA| = |λ|
|OB| = 1
OA.OB =|OA|OB|cosx
=> (λcosa,λsina).(-sinβ,cosβ) = |λ|cosx
-λcosasinβ+λsinacosβ= |λ|cosx
λsin(a-β) = |λ|cosx
λsinπ/6 = |λ|cosx
λ/2 = |λ|cosx
cosx = 1/2 or -1/2
x = π/3 or 2π/3
(2)
|OA| ≥2|OB|
=> |λ| ≥2
=> λ ≥2 or λ