Database
SUPPLEMENTARY MATERIAL (USERS' MATHBOXES)
Mathbox for Richard Penner
Exploring Topology via Seifert and Threlfall
Equinumerosity of sets of relations and maps
rfovcnvd
Metamath Proof Explorer
Description: Value of the converse of the operator, ( A O B ) , which maps
between relations and functions for relations between base sets,
A and B . (Contributed by RP , 27-Apr-2021)
Ref
Expression
Hypotheses
rfovd.rf
⊢ O = a ∈ V , b ∈ V ⟼ r ∈ 𝒫 a × b ⟼ x ∈ a ⟼ y ∈ b | x r y
rfovd.a
⊢ φ → A ∈ V
rfovd.b
⊢ φ → B ∈ W
rfovcnvf1od.f
⊢ F = A O B
Assertion
rfovcnvd
⊢ φ → F -1 = f ∈ 𝒫 B A ⟼ x y | x ∈ A ∧ y ∈ f ⁡ x
Proof
Step
Hyp
Ref
Expression
1
rfovd.rf
⊢ O = a ∈ V , b ∈ V ⟼ r ∈ 𝒫 a × b ⟼ x ∈ a ⟼ y ∈ b | x r y
2
rfovd.a
⊢ φ → A ∈ V
3
rfovd.b
⊢ φ → B ∈ W
4
rfovcnvf1od.f
⊢ F = A O B
5
1 2 3 4
rfovcnvf1od
⊢ φ → F : 𝒫 A × B ⟶ 1-1 onto 𝒫 B A ∧ F -1 = f ∈ 𝒫 B A ⟼ x y | x ∈ A ∧ y ∈ f ⁡ x
6
5
simprd
⊢ φ → F -1 = f ∈ 𝒫 B A ⟼ x y | x ∈ A ∧ y ∈ f ⁡ x