English
The comultiplication on a product is given by splitting and mapping each component.
Русский
Копуляция на произведении даётся отображением компонент.
LaTeX
$$$\\text{comul}(a,b) = \\mathrm{TensorProduct.map}(\\mathrm{inl},\\mathrm{inl}) (\\text{comul}(a)) + \\mathrm{TensorProduct.map}(\\mathrm{inr},\\mathrm{inr}) (\\text{comul}(b)).$$$
Lean4
@[simp]
theorem comul_apply (r : A × B) :
comul r =
TensorProduct.map (.inl R A B) (.inl R A B) (comul r.1) +
TensorProduct.map (.inr R A B) (.inr R A B) (comul r.2) :=
rfl