English
A multiplicative homomorphism f preserves multiplication: f(xy) = f(x) f(y) for all x,y.
Русский
Гомоморфизм умножения f сохраняет умножение: f(xy) = f(x) f(y) для всех x,y.
LaTeX
$$$ f(xy) = f(x) f(y) $$$
Lean4
/-- See note [hom simp lemma priority] -/
@[to_additive (attr := simp mid)]
theorem map_mul [MulHomClass F M N] (f : F) (x y : M) : f (x * y) = f x * f y :=
MulHomClass.map_mul f x y