Module: Mathlib.RingTheory.HahnSeries.HahnEmbedding

Goal state before:
pp: M : Type u_1
inst✝² : AddCommGroup M
inst✝¹ : LinearOrder M
inst✝ : IsOrderedAddMonoid M
f₁ : M →+o DivisibleHull M := DivisibleHull.coeOrderAddMonoidHom M
hf₁ : Function.Injective ⇑f₁
hf₁class :
  ∀ (a : M), ArchimedeanClass.mk a = (DivisibleHull.archimedeanClassOrderIso M).symm (ArchimedeanClass.mk (f₁ a))
f₂' : DivisibleHull M →ₗ[ℚ] Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧
hf₂' : StrictMono ⇑f₂'
hf₂class' :
  ∀ (a : DivisibleHull M),
    ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso (DivisibleHull M)) (ofLex (f₂' a)).orderTop
f₂ : DivisibleHull M →+o Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧ :=
  { toAddMonoidHom := f₂'.toAddMonoidHom, monotone' := ⋯ }
hf₂ : Function.Injective ⇑f₂
hf₂class :
  ∀ (a : DivisibleHull M),
    ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso (DivisibleHull M)) (ofLex (f₂ a)).orderTop
f₃ : Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧ →+o Lex ℝ⟦FiniteArchimedeanClass M⟧ :=
  embDomainOrderAddMonoidHom
    (RelIso.toRelEmbedding (FiniteArchimedeanClass.congrOrderIso (DivisibleHull.archimedeanClassOrderIso M).symm))
hf₃ : Function.Injective ⇑f₃
⊢ ∃ f,
    Function.Injective ⇑f ∧
      ∀ (a : M), ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso M) (ofLex (f a)).orderTop

Tactic:
have hf₃class (a : Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧) :
      (ofLex a).orderTop = OrderIso.withTopCongr
      ((FiniteArchimedeanClass.congrOrderIso (DivisibleHull.archimedeanClassOrderIso M)))
      (ofLex (f₃ a)).orderTop := by
    rw [← OrderIso.symm_apply_eq]
    simp [f₃, ← OrderIso.withTopCongr_symm]

Goal state after:
M : Type u_1
inst✝² : AddCommGroup M
inst✝¹ : LinearOrder M
inst✝ : IsOrderedAddMonoid M
f₁ : M →+o DivisibleHull M := DivisibleHull.coeOrderAddMonoidHom M
hf₁ : Function.Injective ⇑f₁
hf₁class :
  ∀ (a : M), ArchimedeanClass.mk a = (DivisibleHull.archimedeanClassOrderIso M).symm (ArchimedeanClass.mk (f₁ a))
f₂' : DivisibleHull M →ₗ[ℚ] Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧
hf₂' : StrictMono ⇑f₂'
hf₂class' :
  ∀ (a : DivisibleHull M),
    ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso (DivisibleHull M)) (ofLex (f₂' a)).orderTop
f₂ : DivisibleHull M →+o Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧ :=
  { toAddMonoidHom := f₂'.toAddMonoidHom, monotone' := ⋯ }
hf₂ : Function.Injective ⇑f₂
hf₂class :
  ∀ (a : DivisibleHull M),
    ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso (DivisibleHull M)) (ofLex (f₂ a)).orderTop
f₃ : Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧ →+o Lex ℝ⟦FiniteArchimedeanClass M⟧ :=
  embDomainOrderAddMonoidHom
    (RelIso.toRelEmbedding (FiniteArchimedeanClass.congrOrderIso (DivisibleHull.archimedeanClassOrderIso M).symm))
hf₃ : Function.Injective ⇑f₃
hf₃class :
  ∀ (a : Lex ℝ⟦FiniteArchimedeanClass (DivisibleHull M)⟧),
    (ofLex a).orderTop =
      (FiniteArchimedeanClass.congrOrderIso (DivisibleHull.archimedeanClassOrderIso M)).withTopCongr
        (ofLex (f₃ a)).orderTop
⊢ ∃ f,
    Function.Injective ⇑f ∧
      ∀ (a : M), ArchimedeanClass.mk a = (FiniteArchimedeanClass.withTopOrderIso M) (ofLex (f a)).orderTop