English
The left unit acts as the identity for the pointwise product with any filter l on β: (1 : Filter α) ×ˢ l = map (1, ·) l.
Русский
Левая единица служит тождественным элементом для точечного произведения с любым фильтром l на β: (1 : Filter α) ×ˢ l = map (1, ·) l.
LaTeX
$$$(1 : Filter \\alpha) \\timesˢ l = \\mathrm{map}( (1,\\cdot) )\, l$$$
Lean4
@[to_additive (attr := simp) zero_prod]
theorem one_prod {l : Filter β} : (1 : Filter α) ×ˢ l = map (1, ·) l :=
pure_prod