Theorem: FractionalIdeal.absNorm_div_norm_eq_absNorm_div_norm
File: Mathlib/RingTheory/FractionalIdeal/Norm.lean

tactic: rw [div_eq_div_iff]
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑(Ideal.absNorm I.num) / ↑|(Algebra.norm ℤ) ↑I.den| = ↑(Ideal.absNorm I₀) / ↑|(Algebra.norm ℤ) ↑a|
state_after: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|

case hb
R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑|(Algebra.norm ℤ) ↑I.den| ≠ 0

case hd
R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑|(Algebra.norm ℤ) ↑a| ≠ 0

tactic: all_goals simpa [Algebra.norm_eq_zero_iff] using nonZeroDivisors.coe_ne_zero _
state_before: case hb
R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑|(Algebra.norm ℤ) ↑I.den| ≠ 0

case hd
R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑|(Algebra.norm ℤ) ↑a| ≠ 0
state_after: no goals

tactic: dsimp only at h h'
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : (fun x => I.den • x) (a • ↑I) = (fun x => I.den • x) (Submodule.map (Algebra.linearMap R K) I₀)
h' : (fun x => a • x) (I.den • ↑I) = (fun x => a • x) (Submodule.map (Algebra.linearMap R K) I.num)
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|
state_after: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : I.den • a • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : a • I.den • ↑I = a • Submodule.map (Algebra.linearMap R K) I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|

tactic: rw [smul_comm] at h
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : I.den • a • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : a • I.den • ↑I = a • Submodule.map (Algebra.linearMap R K) I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|
state_after: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : a • I.den • ↑I = a • Submodule.map (Algebra.linearMap R K) I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|

tactic: rw [h, Submonoid.smul_def, Submonoid.smul_def, ← Submodule.ideal_span_singleton_smul,
  ← Submodule.ideal_span_singleton_smul, ← Submodule.map_smul'', ← Submodule.map_smul'',
  (LinearMap.map_injective ?_).eq_iff, smul_eq_mul, smul_eq_mul] at h'
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : a • I.den • ↑I = a • Submodule.map (Algebra.linearMap R K) I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|
state_after: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : Ideal.span {↑I.den} * I₀ = Ideal.span {↑a} * I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|

R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' :
  Submodule.map (Algebra.linearMap R K) (Ideal.span {↑I.den} • I₀) =
    Submodule.map (Algebra.linearMap R K) (Ideal.span {↑a} • I.num)
⊢ LinearMap.ker (Algebra.linearMap R K) = ⊥

tactic: simp_rw [← Int.cast_natAbs, ← Nat.cast_mul, ← Ideal.absNorm_span_singleton]
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : Ideal.span {↑I.den} * I₀ = Ideal.span {↑a} * I.num
⊢ ↑(Ideal.absNorm I.num) * ↑|(Algebra.norm ℤ) ↑a| = ↑(Ideal.absNorm I₀) * ↑|(Algebra.norm ℤ) ↑I.den|
state_after: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : Ideal.span {↑I.den} * I₀ = Ideal.span {↑a} * I.num
⊢ ↑(Ideal.absNorm I.num * Ideal.absNorm (Ideal.span {↑a})) = ↑(Ideal.absNorm I₀ * Ideal.absNorm (Ideal.span {↑I.den}))

tactic: rw [← _root_.map_mul, ← _root_.map_mul, mul_comm, ← h', mul_comm]
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' : Ideal.span {↑I.den} * I₀ = Ideal.span {↑a} * I.num
⊢ ↑(Ideal.absNorm I.num * Ideal.absNorm (Ideal.span {↑a})) = ↑(Ideal.absNorm I₀ * Ideal.absNorm (Ideal.span {↑I.den}))
state_after: no goals

tactic: exact LinearMap.ker_eq_bot.mpr (IsFractionRing.injective R K)
state_before: R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • I.den • ↑I = I.den • Submodule.map (Algebra.linearMap R K) I₀
h' :
  Submodule.map (Algebra.linearMap R K) (Ideal.span {↑I.den} • I₀) =
    Submodule.map (Algebra.linearMap R K) (Ideal.span {↑a} • I.num)
⊢ LinearMap.ker (Algebra.linearMap R K) = ⊥
state_after: no goals

tactic: simpa [Algebra.norm_eq_zero_iff] using nonZeroDivisors.coe_ne_zero _
state_before: case hd
R : Type u_1
inst✝⁶ : CommRing R
inst✝⁵ : IsDedekindDomain R
inst✝⁴ : Module.Free ℤ R
inst✝³ : Module.Finite ℤ R
K : Type u_2
inst✝² : CommRing K
inst✝¹ : Algebra R K
inst✝ : IsFractionRing R K
I : FractionalIdeal R⁰ K
a : ↥R⁰
I₀ : Ideal R
h : a • ↑I = Submodule.map (Algebra.linearMap R K) I₀
⊢ ↑|(Algebra.norm ℤ) ↑a| ≠ 0
state_after: no goals