English
The function sending (x,y) to x + y on a module M is linear over R; in particular, addition on the product M × M is linear.
Русский
Функция, отправляющая пары (x,y) в x + y на модуле M, линейна над R; в частности, сложение на произведении M × M линейно.
LaTeX
$$IsLinearMap R (fun x : M × M => x.1 + x.2)$$
Lean4
theorem isLinearMap_add [AddCommMonoid M] [Module R M] : IsLinearMap R fun x : M × M => x.1 + x.2 :=
by
apply IsLinearMap.mk
· intro x y
simp only [Prod.fst_add, Prod.snd_add]
abel
· simp [smul_add]