English
If M acts faithfully on α and β is nonempty, then the induced action of M on α×β is faithful in the left coordinate.
Русский
Если M действует верно на α и β непусто, то на α×β действует верно по левой координате.
LaTeX
$$$[FaithfulSMul M α]\\, [Nonempty β] \\Rightarrow FaithfulSMul M (α × β)$$$
Lean4
@[to_additive]
instance faithfulSMulLeft [FaithfulSMul M α] [Nonempty β] : FaithfulSMul M (α × β) where
eq_of_smul_eq_smul
h :=
let ⟨b⟩ := ‹Nonempty β›
eq_of_smul_eq_smul fun a : α => by injection h (a, b)