曲线((ρ(θ);θ), θ, α, β)
曲线((a sin(3θ); θ), θ, 0, 2π)
曲线((a sin(2θ); θ), θ, 0, 2π)
ρ
2
=
a
2
s
i
n
(
2
θ
)
ρ^2=a^2sin(2θ)
ρ2=a2sin(2θ)
曲线((a sqrt(sin(2θ)); θ), θ, 0, 2π)