Module: Mathlib.Topology.Homotopy.Lifting

Goal state before:
pp: case e'_1
E : Type u_1
X : Type u_2
A : Type u_3
inst✝² : TopologicalSpace E
inst✝¹ : TopologicalSpace X
inst✝ : TopologicalSpace A
p : E → X
f : C(↑I × A, X)
g : ↑I × A → E
g_lifts : p ∘ g = ⇑f
cont_0 : Continuous[inst✝, inst✝²] fun x ↦ g (0, x)
a : A
cont_a : Continuous[_, inst✝²] fun x ↦ g (x, a)
q : E → OpenPartialHomeomorph E X
mem_source : ∀ (x : E), x ∈ (q x).source
hpq : ∀ (x : E), p = ↑(q x)
t : ℕ → ↑I
t_0 : t 0 = 0
t_mono : Monotone t
t_sub : ∀ (n : ℕ), ∃ i, Set.Icc (t n) (t (n + 1)) ⊆ (fun x ↦ g (x, a)) ⁻¹' (q i).source
n_max : ℕ
h_max : ∀ m ≥ n_max, t m = 1
this :
  ∀ (n : ℕ),
    ∃ N,
      a ∈ N ∧
        IsOpen[inst✝] N ∧
          ∃ g',
            ContinuousOn g' (Set.Icc 0 (t n) ×ˢ N) ∧
              p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ t n, g' (t', a) = g (t', a)
N : Set A
haN : a ∈ N
N_open : IsOpen[inst✝] N
hN :
  ∃ g',
    ContinuousOn g' (Set.Icc 0 1 ×ˢ N) ∧
      p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ 1, g' (t', a) = g (t', a)
x✝ : ↑I × A → E
⊢ Set.univ = Set.Icc 0 1

pp: case e'_2
E : Type u_1
X : Type u_2
A : Type u_3
inst✝² : TopologicalSpace E
inst✝¹ : TopologicalSpace X
inst✝ : TopologicalSpace A
p : E → X
f : C(↑I × A, X)
g : ↑I × A → E
g_lifts : p ∘ g = ⇑f
cont_0 : Continuous[inst✝, inst✝²] fun x ↦ g (0, x)
a : A
cont_a : Continuous[_, inst✝²] fun x ↦ g (x, a)
q : E → OpenPartialHomeomorph E X
mem_source : ∀ (x : E), x ∈ (q x).source
hpq : ∀ (x : E), p = ↑(q x)
t : ℕ → ↑I
t_0 : t 0 = 0
t_mono : Monotone t
t_sub : ∀ (n : ℕ), ∃ i, Set.Icc (t n) (t (n + 1)) ⊆ (fun x ↦ g (x, a)) ⁻¹' (q i).source
n_max : ℕ
h_max : ∀ m ≥ n_max, t m = 1
this :
  ∀ (n : ℕ),
    ∃ N,
      a ∈ N ∧
        IsOpen[inst✝] N ∧
          ∃ g',
            ContinuousOn g' (Set.Icc 0 (t n) ×ˢ N) ∧
              p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ t n, g' (t', a) = g (t', a)
N : Set A
haN : a ∈ N
N_open : IsOpen[inst✝] N
hN :
  ∃ g',
    ContinuousOn g' (Set.Icc 0 1 ×ˢ N) ∧
      p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ 1, g' (t', a) = g (t', a)
x✝ : ↑I × A → E
a✝ : ↑I
⊢ x✝ (a✝, a) = g (a✝, a) ↔ a✝ ≤ 1 → x✝ (a✝, a) = g (a✝, a)

Tactic:
· rw [eq_comm, Set.eq_univ_iff_forall]; exact fun t ↦ ⟨bot_le, le_top⟩

Goal state after:
case e'_2
E : Type u_1
X : Type u_2
A : Type u_3
inst✝² : TopologicalSpace E
inst✝¹ : TopologicalSpace X
inst✝ : TopologicalSpace A
p : E → X
f : C(↑I × A, X)
g : ↑I × A → E
g_lifts : p ∘ g = ⇑f
cont_0 : Continuous[inst✝, inst✝²] fun x ↦ g (0, x)
a : A
cont_a : Continuous[_, inst✝²] fun x ↦ g (x, a)
q : E → OpenPartialHomeomorph E X
mem_source : ∀ (x : E), x ∈ (q x).source
hpq : ∀ (x : E), p = ↑(q x)
t : ℕ → ↑I
t_0 : t 0 = 0
t_mono : Monotone t
t_sub : ∀ (n : ℕ), ∃ i, Set.Icc (t n) (t (n + 1)) ⊆ (fun x ↦ g (x, a)) ⁻¹' (q i).source
n_max : ℕ
h_max : ∀ m ≥ n_max, t m = 1
this :
  ∀ (n : ℕ),
    ∃ N,
      a ∈ N ∧
        IsOpen[inst✝] N ∧
          ∃ g',
            ContinuousOn g' (Set.Icc 0 (t n) ×ˢ N) ∧
              p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ t n, g' (t', a) = g (t', a)
N : Set A
haN : a ∈ N
N_open : IsOpen[inst✝] N
hN :
  ∃ g',
    ContinuousOn g' (Set.Icc 0 1 ×ˢ N) ∧
      p ∘ g' = ⇑f ∧ (∀ (a : A), g' (0, a) = g (0, a)) ∧ ∀ t' ≤ 1, g' (t', a) = g (t', a)
x✝ : ↑I × A → E
a✝ : ↑I
⊢ x✝ (a✝, a) = g (a✝, a) ↔ a✝ ≤ 1 → x✝ (a✝, a) = g (a✝, a)