English
If f is injective, then leadingCoeff(p.map f) = f(leadingCoeff p) for any p ∈ R[X].
Русский
Если f инъективен, то leadingCoeff(p.map f) = f(leadingCoeff p) для любого p ∈ R[X].
LaTeX
$$$\forall {R} {S} [\text{Semiring } R] [\text{Semiring } S] {f : R \rightarrow+* S} (hf : Injective f) {p : R[X]}, leadingCoeff (p.map f) = f (leadingCoeff p)$$$
Lean4
theorem leadingCoeff_map' (hf : Injective f) (p : R[X]) : leadingCoeff (p.map f) = f (leadingCoeff p) :=
by
unfold leadingCoeff
rw [coeff_map, natDegree_map_eq_of_injective hf p]