English
Let g: β → γ be injective. Then Multipliable (extend g f 1) is equivalent to Multipliable f; extending the index set and filling new spots with 1 preserves multipliability.
Русский
Пусть g: β → γ — инъекция. Тогда Multipliable (extend g f 1) эквивалентно Multipliable f; расширение индексов и заполнение новых позиций единицей сохраняют мультиплиируемость.
LaTeX
$$$\text{Injective } g\;\Rightarrow\; \text{Multipliable } (\text{extend } g\, f\, 1) \iff \text{Multipliable } f$$$
Lean4
@[to_additive (attr := simp)]
theorem multipliable_extend_one {g : β → γ} (hg : Injective g) : Multipliable (extend g f 1) ↔ Multipliable f :=
exists_congr fun _ ↦ hasProd_extend_one hg