Theorem: Pi.lt_toLex_update_self_iff
File: Mathlib/Order/PiLex.lean

Proof steps:
state_before: ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
⊢ toLex x < toLex (update x i a) ↔ x i < a
state_after: ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
⊢ toLex x < toLex (update x i a) → x i < a
tactic: refine ⟨?_, fun h => toLex_strictMono <| lt_update_self_iff.2 h⟩
state_before: ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
⊢ toLex x < toLex (update x i a) → x i < a
state_after: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
j : ι
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x i a) j_1
h : toLex x j < toLex (update x i a) j
⊢ x i < a
tactic: rintro ⟨j, hj, h⟩
state_before: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
j : ι
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x i a) j_1
h : toLex x j < toLex (update x i a) j
⊢ x i < a
state_after: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
j : ι
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x i a) j_1
h : x j < update x i a j
⊢ x i < a
tactic: dsimp at h
state_before: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
i : ι
a : β i
j : ι
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x i a) j_1
h : x j < update x i a j
⊢ x i < a
state_after: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
j : ι
a : β j
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x j a) j_1
h : x j < update x j a j
⊢ x j < a
tactic: obtain rfl : j = i := by
    by_contra H
    rw [update_noteq H] at h
    exact h.false
state_before: case intro.intro
ι : Type u_1
β : ι → Type u_2
r : ι → ι → Prop
s : {i : ι} → β i → β i → Prop
inst✝² : LinearOrder ι
inst✝¹ : IsWellOrder ι fun x x_1 => x < x_1
inst✝ : (i : ι) → PartialOrder (β i)
x y : (i : ι) → β i
j : ι
a : β j
hj : ∀ (j_1 : ι), (fun x x_1 => x < x_1) j_1 j → toLex x j_1 = toLex (update x j a) j_1
h : x j < update x j a j
⊢ x j < a
state_after: no goals
tactic: rwa [update_same] at h