Theorem: Finset.mulEnergy_univ_left
File: Mathlib/Combinatorics/Additive/Energy.lean

Proof steps:
state_before: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
⊢ Eₘ[univ, t] = Fintype.card α * t.card ^ 2
state_after: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
tactic: simp only [mulEnergy, univ_product_univ, Fintype.card, sq, ← card_product]
state_before: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
state_after: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
tactic: let f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
state_before: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
state_after: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
tactic: have : (↑((univ : Finset α) ×ˢ t ×ˢ t) : Set (α × α × α)).InjOn f := by
    rintro ⟨a₁, b₁, c₁⟩ _ ⟨a₂, b₂, c₂⟩ h₂ h
    simp_rw [Prod.ext_iff] at h
    obtain ⟨h, rfl, rfl⟩ := h
    rw [mul_right_cancel h.1]
state_before: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (univ ×ˢ t ×ˢ t).card
state_after: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (image f (univ ×ˢ t ×ˢ t)).card
tactic: rw [← card_image_of_injOn this]
state_before: α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
⊢ (filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t)).card = (image f (univ ×ˢ t ×ˢ t)).card
state_after: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ a ∈ filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t) ↔ a ∈ image f (univ ×ˢ t ×ˢ t)
tactic: congr with a
state_before: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ a ∈ filter (fun x => x.1.1 * x.2.1 = x.1.2 * x.2.2) (univ ×ˢ t ×ˢ t) ↔ a ∈ image f (univ ×ˢ t ×ˢ t)
state_after: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ (a.2.1 ∈ t ∧ a.2.2 ∈ t) ∧ a.1.1 * a.2.1 = a.1.2 * a.2.2 ↔ ∃ a_1 a_2 b, (a_2 ∈ t ∧ b ∈ t) ∧ f (a_1, a_2, b) = a
tactic: simp only [mem_filter, mem_product, mem_univ, true_and_iff, mem_image, exists_prop,
    Prod.exists]
state_before: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ (a.2.1 ∈ t ∧ a.2.2 ∈ t) ∧ a.1.1 * a.2.1 = a.1.2 * a.2.2 ↔ ∃ a_1 a_2 b, (a_2 ∈ t ∧ b ∈ t) ∧ f (a_1, a_2, b) = a
state_after: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ (∃ a_1 a_2 b, (a_2 ∈ t ∧ b ∈ t) ∧ f (a_1, a_2, b) = a) → (a.2.1 ∈ t ∧ a.2.2 ∈ t) ∧ a.1.1 * a.2.1 = a.1.2 * a.2.2
tactic: refine ⟨fun h => ⟨a.1.1 * a.2.2⁻¹, _, _, h.1, by simp [f, mul_right_comm, h.2]⟩, ?_⟩
state_before: case e_s.a
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
a : (α × α) × α × α
⊢ (∃ a_1 a_2 b, (a_2 ∈ t ∧ b ∈ t) ∧ f (a_1, a_2, b) = a) → (a.2.1 ∈ t ∧ a.2.2 ∈ t) ∧ a.1.1 * a.2.1 = a.1.2 * a.2.2
state_after: case e_s.a.intro.intro.intro.intro
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
b c d : α
hcd : c ∈ t ∧ d ∈ t
⊢ ((f (b, c, d)).2.1 ∈ t ∧ (f (b, c, d)).2.2 ∈ t) ∧
    (f (b, c, d)).1.1 * (f (b, c, d)).2.1 = (f (b, c, d)).1.2 * (f (b, c, d)).2.2
tactic: rintro ⟨b, c, d, hcd, rfl⟩
state_before: case e_s.a.intro.intro.intro.intro
α : Type u_1
inst✝² : DecidableEq α
inst✝¹ : CommGroup α
inst✝ : Fintype α
s t : Finset α
f : α × α × α → (α × α) × α × α := fun x => ((x.1 * x.2.2, x.1 * x.2.1), x.2)
this : Set.InjOn f ↑(univ ×ˢ t ×ˢ t)
b c d : α
hcd : c ∈ t ∧ d ∈ t
⊢ ((f (b, c, d)).2.1 ∈ t ∧ (f (b, c, d)).2.2 ∈ t) ∧
    (f (b, c, d)).1.1 * (f (b, c, d)).2.1 = (f (b, c, d)).1.2 * (f (b, c, d)).2.2
state_after: no goals
tactic: simpa [mul_right_comm]