Module: Mathlib.RingTheory.HahnSeries.Multiplication

Goal state before:
pp: Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := { toAddCommMonoid := inst✝².toAddCommMonoid, toIsLeftCancelAdd := ⋯ }
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := this.min hyz
ha : y.coeff a ≠ z.coeff a
⊢ ¬∑ x_1 ∈ antidiagonal ⋯ ⋯ (x.order + a) ∪ ?m.138, x.coeff x_1.1 * y.coeff x_1.2 =
      ∑ ij ∈ antidiagonal ⋯ ⋯ (x.order + a), x.coeff ij.1 * z.coeff ij.2

pp: Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := { toAddCommMonoid := inst✝².toAddCommMonoid, toIsLeftCancelAdd := ⋯ }
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := this.min hyz
ha : y.coeff a ≠ z.coeff a
⊢ ∀ x_1 ∈ antidiagonal ⋯ ⋯ (x.order + a) ∪ ?m.138,
    x_1 ∉ antidiagonal ⋯ ⋯ (x.order + a) → x.coeff x_1.1 * y.coeff x_1.2 = 0

pp: Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := ⋯
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := ⋯
ha : y.coeff a ≠ z.coeff a
⊢ Finset (Γ × Γ)

Tactic:
sum_subset (s₁ := antidiagonal _ _ _) subset_union_right,

Goal state after:
Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := { toAddCommMonoid := inst✝².toAddCommMonoid, toIsLeftCancelAdd := ⋯ }
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := this.min hyz
ha : y.coeff a ≠ z.coeff a
⊢ ¬∑ x_1 ∈ antidiagonal ⋯ ⋯ (x.order + a) ∪ ?m.138, x.coeff x_1.1 * y.coeff x_1.2 =
      ∑ x_1 ∈ ?m.157 ∪ antidiagonal ⋯ ⋯ (x.order + a), x.coeff x_1.1 * z.coeff x_1.2

Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := { toAddCommMonoid := inst✝².toAddCommMonoid, toIsLeftCancelAdd := ⋯ }
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := this.min hyz
ha : y.coeff a ≠ z.coeff a
⊢ ∀ x_1 ∈ ?m.157 ∪ antidiagonal ⋯ ⋯ (x.order + a),
    x_1 ∉ antidiagonal ⋯ ⋯ (x.order + a) → x.coeff x_1.1 * z.coeff x_1.2 = 0

Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := ⋯
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := ⋯
ha : y.coeff a ≠ z.coeff a
⊢ Finset (Γ × Γ)

Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := { toAddCommMonoid := inst✝².toAddCommMonoid, toIsLeftCancelAdd := ⋯ }
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := this.min hyz
ha : y.coeff a ≠ z.coeff a
⊢ ∀ x_1 ∈ antidiagonal ⋯ ⋯ (x.order + a) ∪ ?m.138,
    x_1 ∉ antidiagonal ⋯ ⋯ (x.order + a) → x.coeff x_1.1 * y.coeff x_1.2 = 0

Γ : Type u_1
Γ' : Type u_2
R : Type u_3
S : Type u_4
V : Type u_5
inst✝⁵ : AddCommMonoid Γ
inst✝⁴ : LinearOrder Γ
inst✝³ : IsOrderedCancelAddMonoid Γ
inst✝² : NonUnitalNonAssocSemiring R
inst✝¹ : IsCancelAdd R
inst✝ : IsCancelMulZero R
x : R⟦Γ⟧
hx : x ≠ 0
y z : R⟦Γ⟧
this✝ : AddCancelCommMonoid R := ⋯
hyz : ∃ x, ¬y.coeff x = z.coeff x
this : {a | y.coeff a ≠ z.coeff a}.IsWF
a : Γ := ⋯
ha : y.coeff a ≠ z.coeff a
⊢ Finset (Γ × Γ)