Module: Mathlib.Analysis.Calculus.LHopital

Goal state before:
pp: case inl.inl
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : s ∩ Iio a = ∅
hs_Ioi : s ∩ Ioi a = ∅
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

pp: case inl.inr
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : s ∩ Iio a = ∅
hs_Ioi : (s ∩ Ioi a).Nonempty
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

pp: case inr.inl
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : (s ∩ Iio a).Nonempty
hs_Ioi : s ∩ Ioi a = ∅
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

pp: case inr.inr
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : (s ∩ Iio a).Nonempty
hs_Ioi : (s ∩ Ioi a).Nonempty
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

Tactic:
· simp [sdiff_eq, ← Iio_union_Ioi, inter_union_distrib_left, hs_Iio, hs_Ioi]

Goal state after:
case inl.inr
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : s ∩ Iio a = ∅
hs_Ioi : (s ∩ Ioi a).Nonempty
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

case inr.inl
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : (s ∩ Iio a).Nonempty
hs_Ioi : s ∩ Ioi a = ∅
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l

case inr.inr
a : ℝ
l : Filter ℝ
f f' g g' : ℝ → ℝ
s : Set ℝ
hs : Convex ℝ s
hg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, g' x ≠ 0
hfa : Tendsto f (𝓝[s \ {a}] a) (𝓝 0)
hga : Tendsto g (𝓝[s \ {a}] a) (𝓝 0)
hdiv : Tendsto (fun x ↦ f' x / g' x) (𝓝[s \ {a}] a) l
has : a ∈ closure s
h : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, s \ {a} ∈ 𝓝 x
hff' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt f (f' x) x
hgg' : ∀ᶠ (x : ℝ) in 𝓝[s \ {a}] a, HasDerivAt g (g' x) x
hs_Iio : (s ∩ Iio a).Nonempty
hs_Ioi : (s ∩ Ioi a).Nonempty
⊢ Tendsto (fun x ↦ f x / g x) (𝓝[s \ {a}] a) l