xsina-√3y+2=0
y=√3*sina *x/3+2√3/3
设l的倾斜角为α
tanα=√3*sina /3
-1≤sina≤1
则 -√3/3≤tanα≤√3/3
则 {α|5π/6≤α≤π} ∪｛α| 0≤α≤π/6}