ρ=4cos(θ-π/3)展开得：ρ=2cosθ-2√3sinθ,式子两边同时乘以ρ,得ρ^2=2ρcosθ-2√3ρsinθ;因为
ρ^2＝x^2+y^2,ρcosθ=x,ρsinθ=y,则x^2+y^2=2x-2√3y,即（x-1)^2+(y+√3)^2=4