English
Let P and Q be three-dimensional coordinate functions over a commutative ring R. If P and Q are equivalent up to a unit factor (i.e., P ≈ Q), then the vanishing of their Z-coordinates agree: P(z) = 0 if and only if Q(z) = 0.
Русский
Пусть P и Q — функции координат в R^3. Если P и Q эквивеликальны до единичного множителя (P ≈ Q), то нули в координате Z совпадают: P(z) = 0 тогда и только тогда, когда Q(z) = 0.
LaTeX
$$$\forall P,Q: \mathbb{Fin}\,3 \to R,\ (P \approx Q)\ \Rightarrow\ (P(z) = 0 \iff Q(z) = 0)$$$
Lean4
theorem Z_eq_zero_of_equiv {P Q : Fin 3 → R} (h : P ≈ Q) : P z = 0 ↔ Q z = 0 :=
by
rcases h with ⟨_, rfl⟩
simp only [Units.smul_def, smul_fin3_ext, Units.mul_right_eq_zero]