-- Module: Mathlib.LinearAlgebra.CliffordAlgebra.Prod
Goal:
R : Type u_1
M₁ : Type u_2
M₂ : Type u_3
N : Type u_4
inst : CommRing R
inst_1 : AddCommGroup M₁
inst_2 : AddCommGroup M₂
inst_3 : AddCommGroup N
inst_4 : Module R M₁
inst_5 : Module R M₂
inst_6 : Module R N
Q₁ : QuadraticForm R M₁
Q₂ : QuadraticForm R M₂
Qₙ : QuadraticForm R N
f₁ : Q₁ →qᵢ Qₙ
f₂ : Q₂ →qᵢ Qₙ
hf : ∀ (x : M₁) (y : M₂), QuadraticMap.IsOrtho Qₙ ((f₁ : (a : M₁) → N) x) ((f₂ : (a : M₂) → N) y)
m₁ : CliffordAlgebra Q₁
m₂ : CliffordAlgebra Q₂
i₂ : ZMod 2
hm₂ : m₂ ∈ evenOdd Q₂ i₂
m₁' : CliffordAlgebra Q₁
i₁n i : ℕ
x₁ : CliffordAlgebra Q₁
_hx₁ : x₁ ∈ (ι Q₁).range ^ i
ih₁ :
  HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
      ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ) x₁ : CliffordAlgebra Qₙ)
      ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ) =
    HPow.hPow (α := ℤˣ) (-1) (i₂ * (↑i : ZMod 2)) •
      HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
        ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ)
        ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ) x₁ : CliffordAlgebra Qₙ)
v₁ : M₁
mem :
  HPow.hPow (α := ℤˣ) (-1) (i₂ * (↑i : ZMod 2)) •
      HMul.hMul (β := CliffordAlgebra Qₙ)
        (HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
          ((ι Qₙ : (a : N) → CliffordAlgebra Qₙ) ((f₁ : (a : M₁) → N) v₁) : CliffordAlgebra Qₙ)
          ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ))
        ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ) x₁ : CliffordAlgebra Qₙ) =
    HPow.hPow (α := ℤˣ) (-1) (i₂ * (↑i : ZMod 2)) •
      HMul.hMul (β := CliffordAlgebra Qₙ)
        (HPow.hPow (α := ℤˣ) (-1) i₂ •
          HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
            ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ)
            ((ι Qₙ : (a : N) → CliffordAlgebra Qₙ) ((f₁ : (a : M₁) → N) v₁) : CliffordAlgebra Qₙ))
        ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ) x₁ : CliffordAlgebra Qₙ)
⊢ HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
      ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ)
          (HMul.hMul (α := CliffordAlgebra Q₁) ((ι Q₁ : (a : M₁) → CliffordAlgebra Q₁) v₁ : CliffordAlgebra Q₁) x₁) :
        CliffordAlgebra Qₙ)
      ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ) =
    HPow.hPow (α := ℤˣ) (-1) (i₂ * (↑i.succ : ZMod 2)) •
      HMul.hMul (α := CliffordAlgebra Qₙ) (β := CliffordAlgebra Qₙ)
        ((map f₂ : (a : CliffordAlgebra Q₂) → CliffordAlgebra Qₙ) m₂ : CliffordAlgebra Qₙ)
        ((map f₁ : (a : CliffordAlgebra Q₁) → CliffordAlgebra Qₙ)
            (HMul.hMul (α := CliffordAlgebra Q₁) ((ι Q₁ : (a : M₁) → CliffordAlgebra Q₁) v₁ : CliffordAlgebra Q₁) x₁) :
          CliffordAlgebra Qₙ)

Tactic:
rw [map_mul, mul_assoc, ih₁, mul_smul_comm, map_apply_ι, Nat.cast_succ, mul_add_one,
        uzpow_add, mul_smul, ← mul_assoc, ← mul_assoc, ← smul_mul_assoc ((-1) ^ i₂)]

Premises used: Nat.cast_succ, mul_assoc, CliffordAlgebra.map_apply_ι, smul_mul_assoc, map_mul, uzpow_add, HPow.hPow, mul_smul_comm, mul_add_one, OfNat.ofNat, SemigroupAction.mul_smul, Neg.neg