Theorem upgrn0

Description: An edge is a nonempty subset of vertices. (Contributed by Mario Carneiro, 11-Mar-2015) (Revised by AV, 10-Oct-2020)

	Ref	Expression
Hypotheses	isupgr.v	⊢ 𝑉 = ( Vtx ‘ 𝐺 )
	isupgr.e	⊢ 𝐸 = ( iEdg ‘ 𝐺 )
Assertion	upgrn0	⊢ ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ∧ 𝐹 ∈ 𝐴 ) → ( 𝐸 ‘ 𝐹 ) ≠ ∅ )

Proof

Step	Hyp	Ref	Expression
1		isupgr.v	⊢ 𝑉 = ( Vtx ‘ 𝐺 )
2		isupgr.e	⊢ 𝐸 = ( iEdg ‘ 𝐺 )
3		ssrab2	⊢ { 𝑥 ∈ ( 𝒫 𝑉 ∖ { ∅ } ) ∣ ( ♯ ‘ 𝑥 ) ≤ 2 } ⊆ ( 𝒫 𝑉 ∖ { ∅ } )
4	1 2	upgrfn	⊢ ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ) → 𝐸 : 𝐴 ⟶ { 𝑥 ∈ ( 𝒫 𝑉 ∖ { ∅ } ) ∣ ( ♯ ‘ 𝑥 ) ≤ 2 } )
5	4	ffvelrnda	⊢ ( ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ) ∧ 𝐹 ∈ 𝐴 ) → ( 𝐸 ‘ 𝐹 ) ∈ { 𝑥 ∈ ( 𝒫 𝑉 ∖ { ∅ } ) ∣ ( ♯ ‘ 𝑥 ) ≤ 2 } )
6	5	3impa	⊢ ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ∧ 𝐹 ∈ 𝐴 ) → ( 𝐸 ‘ 𝐹 ) ∈ { 𝑥 ∈ ( 𝒫 𝑉 ∖ { ∅ } ) ∣ ( ♯ ‘ 𝑥 ) ≤ 2 } )
7	3 6	sseldi	⊢ ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ∧ 𝐹 ∈ 𝐴 ) → ( 𝐸 ‘ 𝐹 ) ∈ ( 𝒫 𝑉 ∖ { ∅ } ) )
8		eldifsni	⊢ ( ( 𝐸 ‘ 𝐹 ) ∈ ( 𝒫 𝑉 ∖ { ∅ } ) → ( 𝐸 ‘ 𝐹 ) ≠ ∅ )
9	7 8	syl	⊢ ( ( 𝐺 ∈ UPGraph ∧ 𝐸 Fn 𝐴 ∧ 𝐹 ∈ 𝐴 ) → ( 𝐸 ‘ 𝐹 ) ≠ ∅ )