∀ {ι : Type u_2} {N : Type u_1} [inst : TopologicalSpace N] [inst_1 : Monoid N] [ContinuousMul N] [T2Space N]
  {f : ι → Nˣ} {r₁ r₂ : N} {l : Filter ι} [l.NeBot],
  Filter.Tendsto (fun x => ↑(f x)) l (nhds r₁) → Filter.Tendsto (fun x => ↑(f x)⁻¹) l (nhds r₂) → r₁ * r₂ = 1