-- Lean 4 proof step from Mathlib.LinearAlgebra.CliffordAlgebra.SpinGroup (goal)
Goal:
R : Type u_1
inst : CommRing R
M : Type u_2
inst_1 : AddCommGroup M
inst_2 : Module R M
Q : QuadraticForm R M
inst_3 : Invertible (α := R) 2
x_1 x : (CliffordAlgebra Q)ˣ
b a : M
ha : (ι Q : (a : M) → CliffordAlgebra Q) a = (↑x : CliffordAlgebra Q)
this_1 : Invertible (↑x : CliffordAlgebra Q) := x.invertible
this_2 : Invertible (α := CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) a : CliffordAlgebra Q) :=
  Eq.mpr ⋯ this_1
this : Invertible (α := R) ((Q : (a : M) → R) a : R) := invertibleOfInvertibleι Q a
mem :
  HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((involute : (a : CliffordAlgebra Q) → CliffordAlgebra Q) (↑x : CliffordAlgebra Q) : CliffordAlgebra Q)
        ((ι Q : (a : M) → CliffordAlgebra Q) b : CliffordAlgebra Q) *
      @Invertible.invOf _ MulOne.toMul MulOne.toOne (↑x : CliffordAlgebra Q) _ ∈
    (ι Q).range
mem₁ :
  HMul.hMul (β := CliffordAlgebra Q)
      (HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((involute : (a : CliffordAlgebra Q) → CliffordAlgebra Q) ((ι Q : (a : M) → CliffordAlgebra Q) a) :
          CliffordAlgebra Q)
        ((ι Q : (a : M) → CliffordAlgebra Q) b : CliffordAlgebra Q))
      (@Invertible.invOf _ MulOne.toMul MulOne.toOne ((ι Q : (a : M) → CliffordAlgebra Q) a) _ : CliffordAlgebra Q) ∈
    (ι Q).range
mem₂ :
  HMul.hMul (β := CliffordAlgebra Q)
      (HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        (-(ι Q : (a : M) → CliffordAlgebra Q) a : CliffordAlgebra Q)
        ((ι Q : (a : M) → CliffordAlgebra Q) b : CliffordAlgebra Q))
      (@Invertible.invOf _ MulOne.toMul MulOne.toOne ((ι Q : (a : M) → CliffordAlgebra Q) a) _ : CliffordAlgebra Q) ∈
    (ι Q).range
mem₃ :
  -HMul.hMul (β := CliffordAlgebra Q)
        (HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
          ((ι Q : (a : M) → CliffordAlgebra Q) a : CliffordAlgebra Q)
          ((ι Q : (a : M) → CliffordAlgebra Q) b : CliffordAlgebra Q))
        (@Invertible.invOf _ MulOne.toMul MulOne.toOne ((ι Q : (a : M) → CliffordAlgebra Q) a) _ : CliffordAlgebra Q) ∈
    (ι Q).range
mem₄ :
  Membership.mem (α := CliffordAlgebra Q) (ι Q).range
    (-(ι Q : (a : M) → CliffordAlgebra Q)
          (HMul.hMul (α := R) (β := R)
                (@Invertible.invOf _ Distrib.toMul AddMonoidWithOne.toOne ((Q : (a : M) → R) a) _ : R)
                (QuadraticMap.polar (⇑Q : (a : M) → R) a b : R) •
              a -
            b) :
      CliffordAlgebra Q)
⊢ HMul.hMul (α := CliffordAlgebra Q) (β := CliffordAlgebra Q)
        ((involute : (a : CliffordAlgebra Q) → CliffordAlgebra Q) (↑x : CliffordAlgebra Q) : CliffordAlgebra Q)
        ((ι Q : (a : M) → CliffordAlgebra Q) b : CliffordAlgebra Q) *
      (↑x⁻¹ : CliffordAlgebra Q) ∈
    (ι Q).range
have mem₅ : Membership.mem (α := CliffordAlgebra Q) (ι Q).range
  ((ι Q : (a : M) → CliffordAlgebra Q)
      (-(HMul.hMul (α := R) (β := R)
              (@Invertible.invOf _ Distrib.toMul AddMonoidWithOne.toOne ((Q : (a : M) → R) a) _ : R)
              (QuadraticMap.polar (⇑Q : (a : M) → R) a b : R) •
            a -
          b)) :
    CliffordAlgebra Q)
Tactic: simp_rw [← invOf_units x, ← ha, involute_ι, neg_mul, ι_mul_ι_mul_invOf_ι Q a b, ← map_neg,
      LinearMap.mem_range_self]