Theorem: deriv.lhopital_zero_atTop
File: Mathlib/Analysis/Calculus/LHopital.lean

Proof steps:
state_before: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
⊢ Tendsto (fun x => f x / g x) atTop l
state_after: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
⊢ Tendsto (fun x => f x / g x) atTop l
tactic: have hdg : ∀ᶠ x in atTop, DifferentiableAt ℝ g x := hg'.mp
    (eventually_of_forall fun _ hg' =>
      by_contradiction fun h => hg' (deriv_zero_of_not_differentiableAt h))
state_before: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
⊢ Tendsto (fun x => f x / g x) atTop l
state_after: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
hdf' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt f (deriv f x) x
⊢ Tendsto (fun x => f x / g x) atTop l
tactic: have hdf' : ∀ᶠ x in atTop, HasDerivAt f (deriv f x) x :=
    hdf.mp (eventually_of_forall fun _ => DifferentiableAt.hasDerivAt)
state_before: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
hdf' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt f (deriv f x) x
⊢ Tendsto (fun x => f x / g x) atTop l
state_after: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
hdf' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt f (deriv f x) x
hdg' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt g (deriv g x) x
⊢ Tendsto (fun x => f x / g x) atTop l
tactic: have hdg' : ∀ᶠ x in atTop, HasDerivAt g (deriv g x) x :=
    hdg.mp (eventually_of_forall fun _ => DifferentiableAt.hasDerivAt)
state_before: a b : ℝ
hab : a < b
l : Filter ℝ
f f' g g' : ℝ → ℝ
hdf : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ f x
hg' : ∀ᶠ (x : ℝ) in atTop, deriv g x ≠ 0
hftop : Tendsto f atTop (𝓝 0)
hgtop : Tendsto g atTop (𝓝 0)
hdiv : Tendsto (fun x => deriv f x / deriv g x) atTop l
hdg : ∀ᶠ (x : ℝ) in atTop, DifferentiableAt ℝ g x
hdf' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt f (deriv f x) x
hdg' : ∀ᶠ (x : ℝ) in atTop, HasDerivAt g (deriv g x) x
⊢ Tendsto (fun x => f x / g x) atTop l
state_after: no goals
tactic: exact HasDerivAt.lhopital_zero_atTop hdf' hdg' hg' hftop hgtop hdiv