Module: Mathlib.LinearAlgebra.CliffordAlgebra.EvenEquiv

Goal state before:
pp: case refine_1
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
f : M × R →ₗ[R] M × R →ₗ[R] CliffordAlgebra Q :=
  ((Algebra.lmul R (CliffordAlgebra Q)).toLinearMap ∘ₗ
        (ι Q ∘ₗ LinearMap.fst R M R + Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)).compl₂
    (ι Q ∘ₗ LinearMap.fst R M R - Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)
f_apply :
  ∀ (x y : M × R),
    (f x) y =
      ((ι Q) x.1 + (algebraMap R (CliffordAlgebra Q)) x.2) * ((ι Q) y.1 - (algebraMap R (CliffordAlgebra Q)) y.2)
hc : ∀ (r : R) (x : CliffordAlgebra Q), Commute ((algebraMap R (CliffordAlgebra Q)) r) x
hm :
  ∀ (m : M × R),
    (ι Q) m.1 * (ι Q) m.1 - (algebraMap R (CliffordAlgebra Q)) m.2 * (algebraMap R (CliffordAlgebra Q)) m.2 =
      (algebraMap R (CliffordAlgebra Q)) ((Q' Q) m)
⊢ ∀ (m : M × R),
    ((ι Q) m.1 + (algebraMap R (CliffordAlgebra Q)) m.2) * ((ι Q) m.1 - (algebraMap R (CliffordAlgebra Q)) m.2) =
      (algebraMap R (CliffordAlgebra Q)) ((Q' Q) m)

pp: case refine_2
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
f : M × R →ₗ[R] M × R →ₗ[R] CliffordAlgebra Q :=
  ((Algebra.lmul R (CliffordAlgebra Q)).toLinearMap ∘ₗ
        (ι Q ∘ₗ LinearMap.fst R M R + Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)).compl₂
    (ι Q ∘ₗ LinearMap.fst R M R - Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)
f_apply :
  ∀ (x y : M × R),
    (f x) y =
      ((ι Q) x.1 + (algebraMap R (CliffordAlgebra Q)) x.2) * ((ι Q) y.1 - (algebraMap R (CliffordAlgebra Q)) y.2)
hc : ∀ (r : R) (x : CliffordAlgebra Q), Commute ((algebraMap R (CliffordAlgebra Q)) r) x
hm :
  ∀ (m : M × R),
    (ι Q) m.1 * (ι Q) m.1 - (algebraMap R (CliffordAlgebra Q)) m.2 * (algebraMap R (CliffordAlgebra Q)) m.2 =
      (algebraMap R (CliffordAlgebra Q)) ((Q' Q) m)
⊢ ∀ (m₁ m₂ m₃ : M × R),
    ((ι Q) m₁.1 + (algebraMap R (CliffordAlgebra Q)) m₁.2) * ((ι Q) m₂.1 - (algebraMap R (CliffordAlgebra Q)) m₂.2) *
        (((ι Q) m₂.1 + (algebraMap R (CliffordAlgebra Q)) m₂.2) *
          ((ι Q) m₃.1 - (algebraMap R (CliffordAlgebra Q)) m₃.2)) =
      (Q' Q) m₂ •
        (((ι Q) m₁.1 + (algebraMap R (CliffordAlgebra Q)) m₁.2) *
          ((ι Q) m₃.1 - (algebraMap R (CliffordAlgebra Q)) m₃.2))

Tactic:
· intro m
    rw [← (hc _ _).symm.mul_self_sub_mul_self_eq, hm]

Goal state after:
case refine_2
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
f : M × R →ₗ[R] M × R →ₗ[R] CliffordAlgebra Q :=
  ((Algebra.lmul R (CliffordAlgebra Q)).toLinearMap ∘ₗ
        (ι Q ∘ₗ LinearMap.fst R M R + Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)).compl₂
    (ι Q ∘ₗ LinearMap.fst R M R - Algebra.linearMap R (CliffordAlgebra Q) ∘ₗ LinearMap.snd R M R)
f_apply :
  ∀ (x y : M × R),
    (f x) y =
      ((ι Q) x.1 + (algebraMap R (CliffordAlgebra Q)) x.2) * ((ι Q) y.1 - (algebraMap R (CliffordAlgebra Q)) y.2)
hc : ∀ (r : R) (x : CliffordAlgebra Q), Commute ((algebraMap R (CliffordAlgebra Q)) r) x
hm :
  ∀ (m : M × R),
    (ι Q) m.1 * (ι Q) m.1 - (algebraMap R (CliffordAlgebra Q)) m.2 * (algebraMap R (CliffordAlgebra Q)) m.2 =
      (algebraMap R (CliffordAlgebra Q)) ((Q' Q) m)
⊢ ∀ (m₁ m₂ m₃ : M × R),
    ((ι Q) m₁.1 + (algebraMap R (CliffordAlgebra Q)) m₁.2) * ((ι Q) m₂.1 - (algebraMap R (CliffordAlgebra Q)) m₂.2) *
        (((ι Q) m₂.1 + (algebraMap R (CliffordAlgebra Q)) m₂.2) *
          ((ι Q) m₃.1 - (algebraMap R (CliffordAlgebra Q)) m₃.2)) =
      (Q' Q) m₂ •
        (((ι Q) m₁.1 + (algebraMap R (CliffordAlgebra Q)) m₁.2) *
          ((ι Q) m₃.1 - (algebraMap R (CliffordAlgebra Q)) m₃.2))