asymptotes in polar form correspond to values t = t0 ∈ R ∪ {±∞}
such that:
• limt→t0 r(t)=±∞;
• limt→t0 θ(t)=α∈R;
• limt→t0 r(t)·(θ(t)−α)∈R.
If these conditions hold, then the asymptote is the line parallel to the line with slope α, at distance δ = limt→t0 r(t) · (θ(t) − α) of the origin.