-- Mathlib/RingTheory/FractionalIdeal/Basic.lean
theorem le_one_iff_exists_coeIdeal {J : FractionalIdeal S P} :
    J ≤ (1 : FractionalIdeal S P) ↔ ∃ I : Ideal R, ↑I = J

Proof state:
case mp.refine_1
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
a b : R
ha : a ∈ {x | (algebraMap R P) x ∈ J}
hb : b ∈ {x | (algebraMap R P) x ∈ J}
⊢ a + b ∈ {x | (algebraMap R P) x ∈ J}

Tactic:
rw [mem_setOf, RingHom.map_add]

Result:
case mp.refine_1
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
a b : R
ha : a ∈ {x | (algebraMap R P) x ∈ J}
hb : b ∈ {x | (algebraMap R P) x ∈ J}
⊢ (algebraMap R P) a + (algebraMap R P) b ∈ J

Proof state:
case mp.refine_4.a.mp.intro.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
y : R
hy : y ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }
eq_y : (Algebra.linearMap R P) y = x
⊢ x ∈ J

Tactic:
rwa [← eq_y]

Result:
no goals

Proof state:
case mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
⊢ (∃ I, ↑I = J) → J ≤ 1

Tactic:
rintro ⟨I, hI⟩

Result:
case mpr.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
I : Ideal R
hI : ↑I = J
⊢ J ≤ 1

Proof state:
case mp.refine_4.a.mpr.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
y : R
hx : (algebraMap R P) y ∈ J
⊢ (algebraMap R P) y ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Tactic:
exact mem_setOf.mpr ⟨y, hx, rfl⟩

Result:
no goals

Proof state:
case mp.refine_2
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
⊢ 0 ∈ { carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯ }.carrier

Tactic:
rw [mem_setOf, RingHom.map_zero]

Result:
case mp.refine_2
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
⊢ 0 ∈ J

Proof state:
case mp.refine_4.a
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ } ↔ x ∈ J

Tactic:
constructor

Result:
case mp.refine_4.a.mp
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ } → x ∈ J

case mp.refine_4.a.mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ J → x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Proof state:
case mp.refine_4.a.mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
hx : x ∈ J
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Tactic:
obtain ⟨y, rfl⟩ := (mem_one_iff S).mp (hJ hx)

Result:
case mp.refine_4.a.mpr.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
y : R
hx : (algebraMap R P) y ∈ J
⊢ (algebraMap R P) y ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Proof state:
case mp.refine_1
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
a b : R
ha : a ∈ {x | (algebraMap R P) x ∈ J}
hb : b ∈ {x | (algebraMap R P) x ∈ J}
⊢ (algebraMap R P) a + (algebraMap R P) b ∈ J

Tactic:
exact J.val.add_mem ha hb

Result:
no goals

Proof state:
case mp.refine_4
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
⊢ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ } = J

Tactic:
ext x

Result:
case mp.refine_4.a
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ } ↔ x ∈ J

Proof state:
case mp
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
⊢ J ≤ 1 → ∃ I, ↑I = J

Tactic:
intro hJ

Result:
case mp
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
⊢ ∃ I, ↑I = J

Proof state:
case mpr.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
I : Ideal R
hI : ↑I = J
⊢ ↑I ≤ 1

Tactic:
apply coeIdeal_le_one

Result:
no goals

Proof state:
case mp.refine_4.a.mp
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ } → x ∈ J

Tactic:
rintro ⟨y, hy, eq_y⟩

Result:
case mp.refine_4.a.mp.intro.intro
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
y : R
hy : y ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }
eq_y : (Algebra.linearMap R P) y = x
⊢ x ∈ J

Proof state:
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
⊢ J ≤ 1 ↔ ∃ I, ↑I = J

Tactic:
constructor

Result:
case mp
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
⊢ J ≤ 1 → ∃ I, ↑I = J

case mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
⊢ (∃ I, ↑I = J) → J ≤ 1

Proof state:
case mp.refine_4.a.mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
⊢ x ∈ J → x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Tactic:
intro hx

Result:
case mp.refine_4.a.mpr
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
x : P
hx : x ∈ J
⊢ x ∈ ↑{ carrier := {x | (algebraMap R P) x ∈ J}, add_mem' := ⋯, zero_mem' := ⋯, smul_mem' := ⋯ }

Proof state:
case mp.refine_1
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
⊢ ∀ {a b : R},
    a ∈ {x | (algebraMap R P) x ∈ J} → b ∈ {x | (algebraMap R P) x ∈ J} → a + b ∈ {x | (algebraMap R P) x ∈ J}

Tactic:
intro a b ha hb

Result:
case mp.refine_1
R : Type u_1
inst✝² : CommRing R
S : Submonoid R
P : Type u_2
inst✝¹ : CommRing P
inst✝ : Algebra R P
J : FractionalIdeal S P
hJ : J ≤ 1
a b : R
ha : a ∈ {x | (algebraMap R P) x ∈ J}
hb : b ∈ {x | (algebraMap R P) x ∈ J}
⊢ a + b ∈ {x | (algebraMap R P) x ∈ J}