Theorem: Monotone.continuousWithinAt_Iio_iff_leftLim_eq
File: Mathlib/Topology/Order/LeftRightLim.lean

Proof steps:
state_before: α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x
state_after: case inl
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x = ⊥
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x

case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x
tactic: rcases eq_or_ne (𝓝[<] x) ⊥ with (h' | h')
state_before: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x
state_after: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this : (𝓝[<] x).NeBot
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x
tactic: haveI : (𝓝[Iio x] x).NeBot := neBot_iff.2 h'
state_before: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this : (𝓝[<] x).NeBot
⊢ ContinuousWithinAt f (Iio x) x ↔ leftLim f x = f x
state_after: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this : (𝓝[<] x).NeBot
h : leftLim f x = f x
⊢ ContinuousWithinAt f (Iio x) x
tactic: refine ⟨fun h => tendsto_nhds_unique (hf.tendsto_leftLim x) h.tendsto, fun h => ?_⟩
state_before: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this : (𝓝[<] x).NeBot
h : leftLim f x = f x
⊢ ContinuousWithinAt f (Iio x) x
state_after: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this✝ : (𝓝[<] x).NeBot
h : leftLim f x = f x
this : Tendsto f (𝓝[<] x) (𝓝 (leftLim f x))
⊢ ContinuousWithinAt f (Iio x) x
tactic: have := hf.tendsto_leftLim x
state_before: case inr
α : Type u_1
β : Type u_2
inst✝⁵ : LinearOrder α
inst✝⁴ : ConditionallyCompleteLinearOrder β
inst✝³ : TopologicalSpace β
inst✝² : OrderTopology β
f : α → β
hf : Monotone f
x y : α
inst✝¹ : TopologicalSpace α
inst✝ : OrderTopology α
h' : 𝓝[<] x ≠ ⊥
this✝ : (𝓝[<] x).NeBot
h : leftLim f x = f x
this : Tendsto f (𝓝[<] x) (𝓝 (leftLim f x))
⊢ ContinuousWithinAt f (Iio x) x
state_after: no goals
tactic: rwa [h] at this