ρ=-cosθ与ρcos(θ+π/3)=1
ρ^2=-ρcosθ与ρcosθcosπ/3-ρsinθsinπ/3=1
x^2+y^2=-x x/2-√3y/2=1
x^2+x+y^2=0 y=x/√3-2/√3
x^2+x+(x/√3-2/√3)^2=0
4x^2-x+4=0
判别式1-32