English
The operation Finset.fin n is monotone with respect to inclusion: s ⊆ t implies s.fin n ⊆ t.fin n.
Русский
Операция Finset.fin n монотонна по включениям: s ⊆ t ⇒ s.fin n ⊆ t.fin n.
LaTeX
$$s \\subseteq t \\Rightarrow s.fin n \\subseteq t.fin n$$
Lean4
@[mono, deprecated attachFin_subset_attachFin (since := "2025-04-08")]
theorem fin_mono : Monotone (Finset.fin n) := fun s t h x => by simpa using @h x