English
If N is IsIsotypic to S and f: M → N is injective, then M is IsIsotypic to S.
Русский
Если N изотипичен к S и существует инъективное отображение M → N, то M изотипичен к S.
LaTeX
$$$IsIsotypic(R, N, S) \land (f : M \to N) \text{ injective} \Rightarrow IsIsotypic(R, M, S)$$$
Lean4
theorem of_injective (h : IsIsotypic R N) (f : M →ₗ[R] N) (inj : Function.Injective f) : IsIsotypic R M := fun m _ ↦
have em := (m.equivMapOfInjective f inj).symm
have := IsSimpleModule.congr em
((h (m.map f)).of_injective f inj).of_linearEquiv_type em