English
There is a canonical algebra homomorphism from S to A over R, built from the tower.
Русский
Существует канонический алгебра-гомоморфизм из S в A над R, построенный из башни.
LaTeX
$$$\mathrm{toAlgHom} : S \to_{\mathbb{R}} A$$$
Lean4
@[ext]
theorem ext {S : Type u} {A : Type v} [CommSemiring S] [Semiring A] (h1 h2 : Algebra S A)
(h : ∀ (r : S) (x : A), (by have I := h1; exact r • x) = r • x) : h1 = h2 :=
Algebra.algebra_ext _ _ fun r => by
simpa only [@Algebra.smul_def _ _ _ _ h1, @Algebra.smul_def _ _ _ _ h2, mul_one] using h r 1