English
Additivity of cast: (cast (a + b : ZMod n) : R) = cast a + cast b.
Русский
Аддитивность приведения: cast(a+b) = cast a + cast b.
LaTeX
$$$\\\\forall {n : \\\\mathbb{N}} {R : Type*} [Ring R] [CharP R n] (a b : ZMod n), \\\\operatorname{cast} (a + b) = \\\\operatorname{cast} a + \\\\operatorname{cast} b$$$
Lean4
theorem cast_add' (a b : ZMod n) : (cast (a + b : ZMod n) : R) = cast a + cast b := by simp