Module: Mathlib.Combinatorics.SimpleGraph.Tutte

Goal state before:
pp: V : Type u_1
G : SimpleGraph V
inst✝ : Finite V
x a b c : V
M1 : (G ⊔ edge x b).Subgraph
M2 : (G ⊔ edge a c).Subgraph
hxa : G.Adj x a
hab : G.Adj a b
hnGxb : ¬G.Adj x b
hnGac : ¬G.Adj a c
hnxb : x ≠ b
hnxc : x ≠ c
hnac : a ≠ c
hnbc : b ≠ c
hM1 : M1.IsPerfectMatching
hM2 : M2.IsPerfectMatching
hM1xb : M1.Adj x b
hM2ac : M2.Adj a c
hM1nac : ¬M1.Adj a c
hsupG : G ⊔ edge x b ⊔ (G ⊔ edge a c) = G ⊔ edge a c ⊔ edge x b
cycles : SimpleGraph V := M1.spanningCoe ∆ M2.spanningCoe
hcalt : cycles.IsAlternating M2.spanningCoe
hcycles : (M1.spanningCoe ∆ M2.spanningCoe).IsCycles
hcac : cycles.Adj a c
hM1sub : M1.spanningCoe ≤ G ⊔ edge x b
hM2sub : M2.spanningCoe ≤ G ⊔ edge a c
induce_le : (cycles.connectedComponentMk c).toSimpleGraph.spanningCoe ≤ G ⊔ edge a c ⊔ edge x b
hxc : x ∈ (cycles.connectedComponentMk c).supp
hacc : a ∈ (cycles.connectedComponentMk c).supp
this : (G : SimpleGraph V) → G.LocallyFinite
hnM2 : ∀ (x' : V), x' ≠ c → ¬M2.Adj x' a
p : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp : p.IsCycle ∧ p.toSubgraph.verts = (cycles.connectedComponentMk c).supp
p' : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp' : p'.IsCycle ∧ p'.snd = c ∧ p'.toSubgraph.verts = p.toSubgraph.verts
x' : V
hx' : x' ∈ {x, b}
hx'p : x' ∈ p'.support
htw : ∀ t ∈ {x, b}, t ∈ (p'.takeUntil x' hx'p).support → t = x'
⊢ ∃ x' ∈ {x, b}, ∃ p, p.IsPath ∧ p.toSubgraph.Adj a c ∧ ¬p.toSubgraph.Adj x b

Tactic:
refine ⟨x', hx', p'.takeUntil x' hx'p, hp'.1.isPath_takeUntil hx'p, ?_, fun h ↦ ?_⟩

Goal state after:
case refine_1
V : Type u_1
G : SimpleGraph V
inst✝ : Finite V
x a b c : V
M1 : (G ⊔ edge x b).Subgraph
M2 : (G ⊔ edge a c).Subgraph
hxa : G.Adj x a
hab : G.Adj a b
hnGxb : ¬G.Adj x b
hnGac : ¬G.Adj a c
hnxb : x ≠ b
hnxc : x ≠ c
hnac : a ≠ c
hnbc : b ≠ c
hM1 : M1.IsPerfectMatching
hM2 : M2.IsPerfectMatching
hM1xb : M1.Adj x b
hM2ac : M2.Adj a c
hM1nac : ¬M1.Adj a c
hsupG : G ⊔ edge x b ⊔ (G ⊔ edge a c) = G ⊔ edge a c ⊔ edge x b
cycles : SimpleGraph V := M1.spanningCoe ∆ M2.spanningCoe
hcalt : cycles.IsAlternating M2.spanningCoe
hcycles : (M1.spanningCoe ∆ M2.spanningCoe).IsCycles
hcac : cycles.Adj a c
hM1sub : M1.spanningCoe ≤ G ⊔ edge x b
hM2sub : M2.spanningCoe ≤ G ⊔ edge a c
induce_le : (cycles.connectedComponentMk c).toSimpleGraph.spanningCoe ≤ G ⊔ edge a c ⊔ edge x b
hxc : x ∈ (cycles.connectedComponentMk c).supp
hacc : a ∈ (cycles.connectedComponentMk c).supp
this : (G : SimpleGraph V) → G.LocallyFinite
hnM2 : ∀ (x' : V), x' ≠ c → ¬M2.Adj x' a
p : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp : p.IsCycle ∧ p.toSubgraph.verts = (cycles.connectedComponentMk c).supp
p' : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp' : p'.IsCycle ∧ p'.snd = c ∧ p'.toSubgraph.verts = p.toSubgraph.verts
x' : V
hx' : x' ∈ {x, b}
hx'p : x' ∈ p'.support
htw : ∀ t ∈ {x, b}, t ∈ (p'.takeUntil x' hx'p).support → t = x'
⊢ (p'.takeUntil x' hx'p).toSubgraph.Adj a c

case refine_2
V : Type u_1
G : SimpleGraph V
inst✝ : Finite V
x a b c : V
M1 : (G ⊔ edge x b).Subgraph
M2 : (G ⊔ edge a c).Subgraph
hxa : G.Adj x a
hab : G.Adj a b
hnGxb : ¬G.Adj x b
hnGac : ¬G.Adj a c
hnxb : x ≠ b
hnxc : x ≠ c
hnac : a ≠ c
hnbc : b ≠ c
hM1 : M1.IsPerfectMatching
hM2 : M2.IsPerfectMatching
hM1xb : M1.Adj x b
hM2ac : M2.Adj a c
hM1nac : ¬M1.Adj a c
hsupG : G ⊔ edge x b ⊔ (G ⊔ edge a c) = G ⊔ edge a c ⊔ edge x b
cycles : SimpleGraph V := M1.spanningCoe ∆ M2.spanningCoe
hcalt : cycles.IsAlternating M2.spanningCoe
hcycles : (M1.spanningCoe ∆ M2.spanningCoe).IsCycles
hcac : cycles.Adj a c
hM1sub : M1.spanningCoe ≤ G ⊔ edge x b
hM2sub : M2.spanningCoe ≤ G ⊔ edge a c
induce_le : (cycles.connectedComponentMk c).toSimpleGraph.spanningCoe ≤ G ⊔ edge a c ⊔ edge x b
hxc : x ∈ (cycles.connectedComponentMk c).supp
hacc : a ∈ (cycles.connectedComponentMk c).supp
this : (G : SimpleGraph V) → G.LocallyFinite
hnM2 : ∀ (x' : V), x' ≠ c → ¬M2.Adj x' a
p : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp : p.IsCycle ∧ p.toSubgraph.verts = (cycles.connectedComponentMk c).supp
p' : (M1.spanningCoe ∆ M2.spanningCoe).Walk a a
hp' : p'.IsCycle ∧ p'.snd = c ∧ p'.toSubgraph.verts = p.toSubgraph.verts
x' : V
hx' : x' ∈ {x, b}
hx'p : x' ∈ p'.support
htw : ∀ t ∈ {x, b}, t ∈ (p'.takeUntil x' hx'p).support → t = x'
h : (p'.takeUntil x' hx'p).toSubgraph.Adj x b
⊢ False