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Metamath Proof Explorer

Theorem umgrf

Description: The edge function of an undirected multigraph is a function into unordered pairs of vertices. Version of umgrfn without explicitly specified domain of the edge function. (Contributed by AV, 24-Nov-2020)

	Ref	Expression
Hypotheses	isumgr.v	⊢ 𝑉 = ( Vtx ‘ 𝐺 )
	isumgr.e	⊢ 𝐸 = ( iEdg ‘ 𝐺 )
Assertion	umgrf	⊢ ( 𝐺 ∈ UMGraph → 𝐸 : dom 𝐸 ⟶ { 𝑥 ∈ 𝒫 𝑉 ∣ ( ♯ ‘ 𝑥 ) = 2 } )

Proof

Step	Hyp	Ref	Expression
1		isumgr.v	⊢ 𝑉 = ( Vtx ‘ 𝐺 )
2		isumgr.e	⊢ 𝐸 = ( iEdg ‘ 𝐺 )
3	1 2	isumgrs	⊢ ( 𝐺 ∈ UMGraph → ( 𝐺 ∈ UMGraph ↔ 𝐸 : dom 𝐸 ⟶ { 𝑥 ∈ 𝒫 𝑉 ∣ ( ♯ ‘ 𝑥 ) = 2 } ) )
4	3	ibi	⊢ ( 𝐺 ∈ UMGraph → 𝐸 : dom 𝐸 ⟶ { 𝑥 ∈ 𝒫 𝑉 ∣ ( ♯ ‘ 𝑥 ) = 2 } )