Theorem: PartialHomeomorph.continuousWithinAt_iff_continuousWithinAt_comp_left
File: Mathlib/Topology/PartialHomeomorph.lean

Proof steps:
state_before: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
⊢ ContinuousWithinAt f s x ↔ ContinuousWithinAt (↑e ∘ f) s x
state_after: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) s x
⊢ ContinuousWithinAt f s x
tactic: refine ⟨(e.continuousAt hx).comp_continuousWithinAt, fun fe_cont => ?_⟩
state_before: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) s x
⊢ ContinuousWithinAt f s x
state_after: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) (s ∩ f ⁻¹' e.source) x
⊢ ContinuousWithinAt f (s ∩ f ⁻¹' e.source) x
tactic: rw [← continuousWithinAt_inter' h] at fe_cont ⊢
state_before: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) (s ∩ f ⁻¹' e.source) x
⊢ ContinuousWithinAt f (s ∩ f ⁻¹' e.source) x
state_after: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) (s ∩ f ⁻¹' e.source) x
this : ContinuousWithinAt (↑e.symm ∘ ↑e ∘ f) (s ∩ f ⁻¹' e.source) x
⊢ ContinuousWithinAt f (s ∩ f ⁻¹' e.source) x
tactic: have : ContinuousWithinAt (e.symm ∘ e ∘ f) (s ∩ f ⁻¹' e.source) x :=
    haveI : ContinuousWithinAt e.symm univ (e (f x)) :=
      (e.continuousAt_symm (e.map_source hx)).continuousWithinAt
    ContinuousWithinAt.comp this fe_cont (subset_univ _)
state_before: X : Type u_1
X' : Type u_2
Y : Type u_3
Y' : Type u_4
Z : Type u_5
Z' : Type u_6
inst✝⁵ : TopologicalSpace X
inst✝⁴ : TopologicalSpace X'
inst✝³ : TopologicalSpace Y
inst✝² : TopologicalSpace Y'
inst✝¹ : TopologicalSpace Z
inst✝ : TopologicalSpace Z'
e : PartialHomeomorph X Y
f : Z → X
s : Set Z
x : Z
hx : f x ∈ e.source
h : f ⁻¹' e.source ∈ 𝓝[s] x
fe_cont : ContinuousWithinAt (↑e ∘ f) (s ∩ f ⁻¹' e.source) x
this : ContinuousWithinAt (↑e.symm ∘ ↑e ∘ f) (s ∩ f ⁻¹' e.source) x
⊢ ContinuousWithinAt f (s ∩ f ⁻¹' e.source) x
state_after: no goals
tactic: exact this.congr (fun y hy => by simp [e.left_inv hy.2]) (by simp [e.left_inv hx])