Theorem: Subsemiring.mem_iSup_of_directed
File: Mathlib/Algebra/Ring/Subsemiring/Basic.lean

tactic: refine ⟨?_, fun ⟨i, hi⟩ ↦ le_iSup S i hi⟩
state_before: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
⊢ x ∈ ⨆ i, S i ↔ ∃ i, x ∈ S i
state_after: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
⊢ x ∈ ⨆ i, S i → ∃ i, x ∈ S i

tactic: let U : Subsemiring R :=
  Subsemiring.mk' (⋃ i, (S i : Set R))
    (⨆ i, (S i).toSubmonoid) (Submonoid.coe_iSup_of_directed hS)
    (⨆ i, (S i).toAddSubmonoid) (AddSubmonoid.coe_iSup_of_directed hS)
state_before: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
⊢ x ∈ ⨆ i, S i → ∃ i, x ∈ S i
state_after: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
U : Subsemiring R := Subsemiring.mk' (⋃ i, ↑(S i)) (⨆ i, (S i).toSubmonoid) ⋯ (⨆ i, (S i).toAddSubmonoid) ⋯
⊢ x ∈ ⨆ i, S i → ∃ i, x ∈ S i

tactic: suffices h : ⨆ i, S i ≤ U by simpa [U] using @h x
state_before: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
U : Subsemiring R := Subsemiring.mk' (⋃ i, ↑(S i)) (⨆ i, (S i).toSubmonoid) ⋯ (⨆ i, (S i).toAddSubmonoid) ⋯
⊢ x ∈ ⨆ i, S i → ∃ i, x ∈ S i
state_after: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
U : Subsemiring R := Subsemiring.mk' (⋃ i, ↑(S i)) (⨆ i, (S i).toSubmonoid) ⋯ (⨆ i, (S i).toAddSubmonoid) ⋯
⊢ ⨆ i, S i ≤ U

tactic: exact iSup_le fun i x hx ↦ Set.mem_iUnion.2 ⟨i, hx⟩
state_before: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
U : Subsemiring R := Subsemiring.mk' (⋃ i, ↑(S i)) (⨆ i, (S i).toSubmonoid) ⋯ (⨆ i, (S i).toAddSubmonoid) ⋯
⊢ ⨆ i, S i ≤ U
state_after: no goals

tactic: simpa [U] using @h x
state_before: R : Type u
S✝ : Type v
T : Type w
inst✝² : NonAssocSemiring R
M : Submonoid R
inst✝¹ : NonAssocSemiring S✝
inst✝ : NonAssocSemiring T
ι : Sort u_1
hι : Nonempty ι
S : ι → Subsemiring R
hS : Directed (fun x x_1 => x ≤ x_1) S
x : R
U : Subsemiring R := Subsemiring.mk' (⋃ i, ↑(S i)) (⨆ i, (S i).toSubmonoid) ⋯ (⨆ i, (S i).toAddSubmonoid) ⋯
h : ⨆ i, S i ≤ U
⊢ x ∈ ⨆ i, S i → ∃ i, x ∈ S i
state_after: no goals