Theorem: DoubleCentralizer.norm_fst_eq_snd
File: Mathlib/Analysis/CstarAlgebra/Multiplier.lean

Proof steps:
state_before: 𝕜 : Type u_1
A : Type u_2
inst✝⁶ : NontriviallyNormedField 𝕜
inst✝⁵ : NonUnitalNormedRing A
inst✝⁴ : NormedSpace 𝕜 A
inst✝³ : SMulCommClass 𝕜 A A
inst✝² : IsScalarTower 𝕜 A A
inst✝¹ : StarRing A
inst✝ : CstarRing A
a : 𝓜(𝕜, A)
h0 : ∀ (f : A →L[𝕜] A) (C : ℝ≥0), (∀ (b : A), ‖f b‖₊ ^ 2 ≤ C * ‖f b‖₊ * ‖b‖₊) → ‖f‖₊ ≤ C
⊢ ‖a.toProd.1‖ = ‖a.toProd.2‖
state_after: 𝕜 : Type u_1
A : Type u_2
inst✝⁶ : NontriviallyNormedField 𝕜
inst✝⁵ : NonUnitalNormedRing A
inst✝⁴ : NormedSpace 𝕜 A
inst✝³ : SMulCommClass 𝕜 A A
inst✝² : IsScalarTower 𝕜 A A
inst✝¹ : StarRing A
inst✝ : CstarRing A
a : 𝓜(𝕜, A)
h0 : ∀ (f : A →L[𝕜] A) (C : ℝ≥0), (∀ (b : A), ‖f b‖₊ ^ 2 ≤ C * ‖f b‖₊ * ‖b‖₊) → ‖f‖₊ ≤ C
h1 : ∀ (b : A), ‖a.toProd.1 b‖₊ ^ 2 ≤ ‖a.toProd.2‖₊ * ‖a.toProd.1 b‖₊ * ‖b‖₊
⊢ ‖a.toProd.1‖ = ‖a.toProd.2‖
tactic: have h1 : ∀ b, ‖a.fst b‖₊ ^ 2 ≤ ‖a.snd‖₊ * ‖a.fst b‖₊ * ‖b‖₊ := by
    intro b
    calc
      ‖a.fst b‖₊ ^ 2 = ‖star (a.fst b) * a.fst b‖₊ := by
        simpa only [← sq] using CstarRing.nnnorm_star_mul_self.symm
      _ ≤ ‖a.snd (star (a.fst b))‖₊ * ‖b‖₊ := (a.central (star (a.fst b)) b ▸ nnnorm_mul_le _ _)
      _ ≤ ‖a.snd‖₊ * ‖a.fst b‖₊ * ‖b‖₊ :=
        nnnorm_star (a.fst b) ▸ mul_le_mul_right' (a.snd.le_opNNNorm _) _
state_before: 𝕜 : Type u_1
A : Type u_2
inst✝⁶ : NontriviallyNormedField 𝕜
inst✝⁵ : NonUnitalNormedRing A
inst✝⁴ : NormedSpace 𝕜 A
inst✝³ : SMulCommClass 𝕜 A A
inst✝² : IsScalarTower 𝕜 A A
inst✝¹ : StarRing A
inst✝ : CstarRing A
a : 𝓜(𝕜, A)
h0 : ∀ (f : A →L[𝕜] A) (C : ℝ≥0), (∀ (b : A), ‖f b‖₊ ^ 2 ≤ C * ‖f b‖₊ * ‖b‖₊) → ‖f‖₊ ≤ C
h1 : ∀ (b : A), ‖a.toProd.1 b‖₊ ^ 2 ≤ ‖a.toProd.2‖₊ * ‖a.toProd.1 b‖₊ * ‖b‖₊
⊢ ‖a.toProd.1‖ = ‖a.toProd.2‖
state_after: 𝕜 : Type u_1
A : Type u_2
inst✝⁶ : NontriviallyNormedField 𝕜
inst✝⁵ : NonUnitalNormedRing A
inst✝⁴ : NormedSpace 𝕜 A
inst✝³ : SMulCommClass 𝕜 A A
inst✝² : IsScalarTower 𝕜 A A
inst✝¹ : StarRing A
inst✝ : CstarRing A
a : 𝓜(𝕜, A)
h0 : ∀ (f : A →L[𝕜] A) (C : ℝ≥0), (∀ (b : A), ‖f b‖₊ ^ 2 ≤ C * ‖f b‖₊ * ‖b‖₊) → ‖f‖₊ ≤ C
h1 : ∀ (b : A), ‖a.toProd.1 b‖₊ ^ 2 ≤ ‖a.toProd.2‖₊ * ‖a.toProd.1 b‖₊ * ‖b‖₊
h2 : ∀ (b : A), ‖a.toProd.2 b‖₊ ^ 2 ≤ ‖a.toProd.1‖₊ * ‖a.toProd.2 b‖₊ * ‖b‖₊
⊢ ‖a.toProd.1‖ = ‖a.toProd.2‖
tactic: have h2 : ∀ b, ‖a.snd b‖₊ ^ 2 ≤ ‖a.fst‖₊ * ‖a.snd b‖₊ * ‖b‖₊ := by
    intro b
    calc
      ‖a.snd b‖₊ ^ 2 = ‖a.snd b * star (a.snd b)‖₊ := by
        simpa only [← sq] using CstarRing.nnnorm_self_mul_star.symm
      _ ≤ ‖b‖₊ * ‖a.fst (star (a.snd b))‖₊ :=
        ((a.central b (star (a.snd b))).symm ▸ nnnorm_mul_le _ _)
      _ = ‖a.fst (star (a.snd b))‖₊ * ‖b‖₊ := mul_comm _ _
      _ ≤ ‖a.fst‖₊ * ‖a.snd b‖₊ * ‖b‖₊ :=
        nnnorm_star (a.snd b) ▸ mul_le_mul_right' (a.fst.le_opNNNorm _) _
state_before: 𝕜 : Type u_1
A : Type u_2
inst✝⁶ : NontriviallyNormedField 𝕜
inst✝⁵ : NonUnitalNormedRing A
inst✝⁴ : NormedSpace 𝕜 A
inst✝³ : SMulCommClass 𝕜 A A
inst✝² : IsScalarTower 𝕜 A A
inst✝¹ : StarRing A
inst✝ : CstarRing A
a : 𝓜(𝕜, A)
h0 : ∀ (f : A →L[𝕜] A) (C : ℝ≥0), (∀ (b : A), ‖f b‖₊ ^ 2 ≤ C * ‖f b‖₊ * ‖b‖₊) → ‖f‖₊ ≤ C
h1 : ∀ (b : A), ‖a.toProd.1 b‖₊ ^ 2 ≤ ‖a.toProd.2‖₊ * ‖a.toProd.1 b‖₊ * ‖b‖₊
h2 : ∀ (b : A), ‖a.toProd.2 b‖₊ ^ 2 ≤ ‖a.toProd.1‖₊ * ‖a.toProd.2 b‖₊ * ‖b‖₊
⊢ ‖a.toProd.1‖ = ‖a.toProd.2‖
state_after: no goals
tactic: exact le_antisymm (h0 _ _ h1) (h0 _ _ h2)