English
Membership equivalence: an element belongs to the groupoid iff the pair (e, source/target) satisfies the pregrouppoid property.
Русский
Принадлежность элементa к групоиду эквивалентна тому, что пара (e, source/target) удовлетворяет свойству pregrouppoid.
LaTeX
$$mem_groupoid_of_pregroupoid {PG : Pregroupoid H} {e : OpenPartialHomeomorph H H} : e ∈ PG.groupoid ↔ PG.property e e.source ∧ PG.property e.symm e.target$$
Lean4
theorem mem_groupoid_of_pregroupoid {PG : Pregroupoid H} {e : OpenPartialHomeomorph H H} :
e ∈ PG.groupoid ↔ PG.property e e.source ∧ PG.property e.symm e.target :=
Iff.rfl