ρ=(2+2cosθ)/sin^2θ
ρsinθ=2(1+cosθ)/sinθ
y=2(cscθ+cotθ)
y=2cscθ+2x/y
y-2x/y=2cscθ
(y-2x/y)^2=4csc^2θ=4(1+cot^2θ)=4(1+x^2/y^2)
化简后为y^2=4x+4
抛物线