-- Mathlib/RingTheory/Artinian/Module.lean
theorem disjoint_partial_infs_eventually_top (f : ℕ → Submodule R M)
    (h : ∀ n, Disjoint (partialSups (OrderDual.toDual ∘ f) n) (OrderDual.toDual (f (n + 1)))) :
    ∃ n : ℕ, ∀ m, n ≤ m → f m = ⊤

Proof state:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → (partialSups (⇑OrderDual.toDual ∘ f)) n = (partialSups (⇑OrderDual.toDual ∘ f)) m
m : ℕ
p : n ≤ m
⊢ (partialSups (⇑OrderDual.toDual ∘ f)) m ⊔ OrderDual.toDual (f (m + 1)) = (partialSups (⇑OrderDual.toDual ∘ f)) m

Tactic:
simpa only [partialSups_add_one] using (w (m + 1) <| le_add_right p).symm.trans <| w m p

Result:
no goals

Proof state:
case h
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
⊢ ∀ (m : ℕ), n + 1 ≤ m → f m = ⊤

Tactic:
rintro (_ | m) p

Result:
case h.zero
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
p : n + 1 ≤ 0
⊢ f 0 = ⊤

case h.succ
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
m : ℕ
p : n + 1 ≤ m + 1
⊢ f (m + 1) = ⊤

Proof state:
case h.zero
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
p : n + 1 ≤ 0
⊢ f 0 = ⊤

Tactic:
cases p

Result:
no goals

Proof state:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → f m = ⊤

Tactic:
use n + 1

Result:
case h
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
⊢ ∀ (m : ℕ), n + 1 ≤ m → f m = ⊤

Proof state:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → (partialSups (⇑OrderDual.toDual ∘ f)) n = (partialSups (⇑OrderDual.toDual ∘ f)) m
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤

Tactic:
refine ⟨n, fun m p ↦ (h m).eq_bot_of_ge <| sup_eq_left.mp ?_⟩

Result:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → (partialSups (⇑OrderDual.toDual ∘ f)) n = (partialSups (⇑OrderDual.toDual ∘ f)) m
m : ℕ
p : n ≤ m
⊢ (partialSups (⇑OrderDual.toDual ∘ f)) m ⊔ OrderDual.toDual (f (m + 1)) = (partialSups (⇑OrderDual.toDual ∘ f)) m

Proof state:
case h.succ
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
m : ℕ
p : n + 1 ≤ m + 1
⊢ f (m + 1) = ⊤

Tactic:
apply w

Result:
case h.succ.a
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
m : ℕ
p : n + 1 ≤ m + 1
⊢ n ≤ m

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤

Tactic:
obtain ⟨n, w⟩ := monotone_stabilizes (partialSups (OrderDual.toDual ∘ f))

Result:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → (partialSups (⇑OrderDual.toDual ∘ f)) n = (partialSups (⇑OrderDual.toDual ∘ f)) m
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤

Proof state:
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → f m = ⊤

Tactic:
rsuffices ⟨n, w⟩ : ∃ n : ℕ, ∀ m, n ≤ m → OrderDual.toDual f (m + 1) = ⊤

Result:
case intro
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → f m = ⊤

R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
⊢ ∃ n, ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤

Proof state:
case h.succ.a
R : Type u_1
M : Type u_2
inst✝³ : Semiring R
inst✝² : AddCommMonoid M
inst✝¹ : Module R M
inst✝ : IsArtinian R M
f : ℕ → Submodule R M
h : ∀ (n : ℕ), Disjoint ((partialSups (⇑OrderDual.toDual ∘ f)) n) (OrderDual.toDual (f (n + 1)))
n : ℕ
w : ∀ (m : ℕ), n ≤ m → OrderDual.toDual f (m + 1) = ⊤
m : ℕ
p : n + 1 ≤ m + 1
⊢ n ≤ m

Tactic:
exact Nat.succ_le_succ_iff.mp p

Result:
no goals