Theorem: is_two_pretransitive_weak_jordan
Proof state before:
n : ℕ
hrec :
  ∀ m < n,
    ∀ {α : Type u_1} {G : Type u_2} [inst : Group G] [inst_1 : MulAction G α] [inst_2 : Fintype α]
      [inst_3 : DecidableEq α],
      IsPreprimitive G α →
        ∀ {s : Set α},
          Set.ncard s = Nat.succ m →
            1 + Nat.succ m < Fintype.card α →
              IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s) → IsMultiplyPretransitive G α 2
α : Type u_1
G : Type u_2
inst✝³ : Group G
inst✝² : MulAction G α
inst✝¹ : Fintype α
inst✝ : DecidableEq α
hG : IsPreprimitive G α
s : Set α
hsn : Set.ncard s = Nat.succ n
hsn' : 1 + Nat.succ n < Fintype.card α
hs_trans : IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s)
hs_ne_top : s ≠ ⊤
hs_nonempty : Set.Nonempty s
hn : Nat.succ n ≥ 2
hn1 : 2 * Nat.succ n < Fintype.card α
a : α
ha : a ∈ s
b : α
hb : b ∈ s
hab : a ≠ b
g : G
hga : a ∈ g • s
hgb : b ∉ g • s
t : Set α := s ∩ g • s
ht_trans : IsPretransitive ↥(fixingSubgroup G t) ↥(SubMulAction.ofFixingSubgroup G t)
this : Set.ncard t ≠ 0
⊢ Set.ncard t < Set.ncard s ∧ Set.ncard t = Set.ncard t
Tactic:
constructor
Proof state after:
case left
n : ℕ
hrec :
  ∀ m < n,
    ∀ {α : Type u_1} {G : Type u_2} [inst : Group G] [inst_1 : MulAction G α] [inst_2 : Fintype α]
      [inst_3 : DecidableEq α],
      IsPreprimitive G α →
        ∀ {s : Set α},
          Set.ncard s = Nat.succ m →
            1 + Nat.succ m < Fintype.card α →
              IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s) → IsMultiplyPretransitive G α 2
α : Type u_1
G : Type u_2
inst✝³ : Group G
inst✝² : MulAction G α
inst✝¹ : Fintype α
inst✝ : DecidableEq α
hG : IsPreprimitive G α
s : Set α
hsn : Set.ncard s = Nat.succ n
hsn' : 1 + Nat.succ n < Fintype.card α
hs_trans : IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s)
hs_ne_top : s ≠ ⊤
hs_nonempty : Set.Nonempty s
hn : Nat.succ n ≥ 2
hn1 : 2 * Nat.succ n < Fintype.card α
a : α
ha : a ∈ s
b : α
hb : b ∈ s
hab : a ≠ b
g : G
hga : a ∈ g • s
hgb : b ∉ g • s
t : Set α := s ∩ g • s
ht_trans : IsPretransitive ↥(fixingSubgroup G t) ↥(SubMulAction.ofFixingSubgroup G t)
this : Set.ncard t ≠ 0
⊢ Set.ncard t < Set.ncard s

case right
n : ℕ
hrec :
  ∀ m < n,
    ∀ {α : Type u_1} {G : Type u_2} [inst : Group G] [inst_1 : MulAction G α] [inst_2 : Fintype α]
      [inst_3 : DecidableEq α],
      IsPreprimitive G α →
        ∀ {s : Set α},
          Set.ncard s = Nat.succ m →
            1 + Nat.succ m < Fintype.card α →
              IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s) → IsMultiplyPretransitive G α 2
α : Type u_1
G : Type u_2
inst✝³ : Group G
inst✝² : MulAction G α
inst✝¹ : Fintype α
inst✝ : DecidableEq α
hG : IsPreprimitive G α
s : Set α
hsn : Set.ncard s = Nat.succ n
hsn' : 1 + Nat.succ n < Fintype.card α
hs_trans : IsPretransitive ↥(fixingSubgroup G s) ↥(SubMulAction.ofFixingSubgroup G s)
hs_ne_top : s ≠ ⊤
hs_nonempty : Set.Nonempty s
hn : Nat.succ n ≥ 2
hn1 : 2 * Nat.succ n < Fintype.card α
a : α
ha : a ∈ s
b : α
hb : b ∈ s
hab : a ≠ b
g : G
hga : a ∈ g • s
hgb : b ∉ g • s
t : Set α := s ∩ g • s
ht_trans : IsPretransitive ↥(fixingSubgroup G t) ↥(SubMulAction.ofFixingSubgroup G t)
this : Set.ncard t ≠ 0
⊢ Set.ncard t = Set.ncard t