ρcosθ=4sinθcosθ
ρ=4sinθ (cosθ≠0）
x=4sinθcosθ
y=4sinθsinθ
x^2+y^2=16(sinθcosθ)^2+16(sinθ)^4
=4*4(sinθ)^2
=4y
x^2+y^2-4y=0
x^2+(y-2)^2=4