-- Mathlib/LinearAlgebra/CliffordAlgebra/Grading.lean
theorem evenOdd_induction (n : ZMod 2) {motive : ∀ x, x ∈ evenOdd Q n → Prop}
    (range_ι_pow : ∀ (v) (h : v ∈ LinearMap.range (ι Q) ^ n.val),
        motive v (Submodule.mem_iSup_of_mem ⟨n.val, n.natCast_zmod_val⟩ h))
    (add : ∀ x y hx hy, motive x hx → motive y hy → motive (x + y) (Submodule.add_mem _ hx hy))
    (ι_mul_ι_mul :
      ∀ m₁ m₂ x hx,
        motive x hx →
          motive (ι Q m₁ * ι Q m₂ * x)
            (zero_add n ▸ SetLike.mul_mem_graded (ι_mul_ι_mem_evenOdd_zero Q m₁ m₂) hx))
    (x : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n) : motive x hx

Proof state:
case intro.add
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
n : ZMod 2
motive : (x : CliffordAlgebra Q) → x ∈ evenOdd Q n → Prop
range_ι_pow : ∀ (v : CliffordAlgebra Q) (h : v ∈ LinearMap.range (ι Q) ^ n.val), motive v ⋯
add :
  ∀ (x y : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n) (hy : y ∈ evenOdd Q n),
    motive x hx → motive y hy → motive (x + y) ⋯
ι_mul_ι_mul :
  ∀ (m₁ m₂ : M) (x : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n), motive x hx → motive ((ι Q) m₁ * (ι Q) m₂ * x) ⋯
x✝ : CliffordAlgebra Q
hx✝ : x✝ ∈ evenOdd Q n
k : ℕ
xv x : CliffordAlgebra Q
y : x ∈ (LinearMap.range (ι Q) ^ 2) ^ k * LinearMap.range (ι Q) ^ n.val
hx : CliffordAlgebra Q
hy : hx ∈ (LinearMap.range (ι Q) ^ 2) ^ k * LinearMap.range (ι Q) ^ n.val
ihx : motive x ⋯
ihy : motive hx ⋯
⊢ motive (x + hx) ⋯

Tactic:
apply add _ _ _ _ ihx ihy

Result:
no goals

Proof state:
case intro.mem_mul_mem.mem_mul.mem_mul_mem.intro
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
n✝ : ZMod 2
motive : (x : CliffordAlgebra Q) → x ∈ evenOdd Q n✝ → Prop
range_ι_pow : ∀ (v : CliffordAlgebra Q) (h : v ∈ LinearMap.range (ι Q) ^ n✝.val), motive v ⋯
add :
  ∀ (x y : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n✝) (hy : y ∈ evenOdd Q n✝),
    motive x hx → motive y hy → motive (x + y) ⋯
ι_mul_ι_mul :
  ∀ (m₁ m₂ : M) (x : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n✝), motive x hx → motive ((ι Q) m₁ * (ι Q) m₂ * x) ⋯
x✝ : CliffordAlgebra Q
hx : x✝ ∈ evenOdd Q n✝
k : ℕ
xv a b : CliffordAlgebra Q
hb : b ∈ LinearMap.range (ι Q) ^ n✝.val
x : CliffordAlgebra Q
n'' : ℕ
y : CliffordAlgebra Q
hy : y ∈ (LinearMap.range (ι Q) ^ 2) ^ n''
ihy : motive (y * b) ⋯
n : CliffordAlgebra Q
hn✝ : n ∈ LinearMap.range (ι Q)
hn : ∃ y, (ι Q) y = n
m₁ : M
hm : (ι Q) m₁ ∈ LinearMap.range (ι Q)
⊢ motive ((ι Q) m₁ * n * y * b) ⋯

Tactic:
obtain ⟨m₂, rfl⟩ := hn

Result:
case intro.mem_mul_mem.mem_mul.mem_mul_mem.intro.intro
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
n : ZMod 2
motive : (x : CliffordAlgebra Q) → x ∈ evenOdd Q n → Prop
range_ι_pow : ∀ (v : CliffordAlgebra Q) (h : v ∈ LinearMap.range (ι Q) ^ n.val), motive v ⋯
add :
  ∀ (x y : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n) (hy : y ∈ evenOdd Q n),
    motive x hx → motive y hy → motive (x + y) ⋯
ι_mul_ι_mul :
  ∀ (m₁ m₂ : M) (x : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n), motive x hx → motive ((ι Q) m₁ * (ι Q) m₂ * x) ⋯
x✝ : CliffordAlgebra Q
hx : x✝ ∈ evenOdd Q n
k : ℕ
xv a b : CliffordAlgebra Q
hb : b ∈ LinearMap.range (ι Q) ^ n.val
x : CliffordAlgebra Q
n'' : ℕ
y : CliffordAlgebra Q
hy : y ∈ (LinearMap.range (ι Q) ^ 2) ^ n''
ihy : motive (y * b) ⋯
m₁ : M
hm : (ι Q) m₁ ∈ LinearMap.range (ι Q)
m₂ : M
hn : (ι Q) m₂ ∈ LinearMap.range (ι Q)
⊢ motive ((ι Q) m₁ * (ι Q) m₂ * y * b) ⋯

Proof state:
case intro.mem_mul_mem.add
R : Type u_1
M : Type u_2
inst✝² : CommRing R
inst✝¹ : AddCommGroup M
inst✝ : Module R M
Q : QuadraticForm R M
n✝ : ZMod 2
motive : (x : CliffordAlgebra Q) → x ∈ evenOdd Q n✝ → Prop
range_ι_pow : ∀ (v : CliffordAlgebra Q) (h : v ∈ LinearMap.range (ι Q) ^ n✝.val), motive v ⋯
add :
  ∀ (x y : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n✝) (hy : y ∈ evenOdd Q n✝),
    motive x hx → motive y hy → motive (x + y) ⋯
ι_mul_ι_mul :
  ∀ (m₁ m₂ : M) (x : CliffordAlgebra Q) (hx : x ∈ evenOdd Q n✝), motive x hx → motive ((ι Q) m₁ * (ι Q) m₂ * x) ⋯
x✝ : CliffordAlgebra Q
hx✝ : x✝ ∈ evenOdd Q n✝
k : ℕ
xv a b : CliffordAlgebra Q
hb : b ∈ LinearMap.range (ι Q) ^ n✝.val
x y : CliffordAlgebra Q
n : ℕ
hx : x ∈ (LinearMap.range (ι Q) ^ 2) ^ n
hy : y ∈ (LinearMap.range (ι Q) ^ 2) ^ n
ihx : motive (x * b) ⋯
ihy : motive (y * b) ⋯
⊢ motive (x * b + y * b) ⋯

Tactic:
apply add _ _ _ _ ihx ihy

Result:
no goals