English
The relation Rel α on pairs in α × α is symmetric: if (x,y) relates to (y,x).
Русский
Отношение Rel α на парах в α × α симметрично: если (x,y) связано с (y,x).
LaTeX
$$$\text{Rel}_{\alpha}(x,y) \Rightarrow \text{Rel}_{\alpha}(y,x)$$$
Lean4
/-- The composition of a `Finsupp` with `Sym2.mul` as a `Finsupp`. -/
noncomputable def sym2Mul (f : α →₀ M₀) : Sym2 α →₀ M₀ :=
.onFinset f.support.sym2 (fun p ↦ mul (p.map f)) mem_sym2_support_of_mul_ne_zero