English
The equality adjoin R s = (Algebra.adjoin R s).starClosure holds, expressing the universal property of star-closure with respect to adjoin.
Русский
Равенство adjoin R s = (Algebra.adjoin R s).starClosure выражает универсальное свойство звёздного замыкания относительно adjoin.
LaTeX
$$$\mathrm{adjoin}(R,s) = (\mathrm{Algebra.adjoin}(R,s)).\mathrm{starClosure}.$$$
Lean4
@[aesop 80% (rule_sets := [SetLike])]
theorem mem_adjoin_of_mem {s : Set A} {x : A} (hx : x ∈ s) : x ∈ adjoin R s :=
subset_adjoin R s hx