English
A relation expresses that the pairing of the chainTopIdx yields a certain integer in the root pairing.
Русский
Связь цепи topIdx выражает, что пара корней через chainTopIdx сопоставляет целое число в pairing.
LaTeX
$$$$ P.chainTopCoeff i j + P.chainBotCoeff i j = P.pairingIn \mathbb{Z} (P.chainTopIdx i j) i $$$$
Lean4
theorem chainBotCoeff_add_chainTopCoeff_eq_pairingIn_chainTopIdx :
P.chainBotCoeff i j + P.chainTopCoeff i j = P.pairingIn ℤ (P.chainTopIdx i j) i :=
by
replace h : LinearIndependent R ![P.root i, P.root (P.chainTopIdx i j)] := by
rwa [P.root_chainTopIdx, add_comm (P.root j), ← natCast_zsmul, LinearIndependent.pair_add_smul_right_iff]
calc
(P.chainBotCoeff i j + P.chainTopCoeff i j : ℤ)
_ = P.chainBotCoeff i (P.chainTopIdx i j) := by simp
_ = P.chainBotCoeff i (P.chainTopIdx i j) - P.chainTopCoeff i (P.chainTopIdx i j) := by simp
_ = P.pairingIn ℤ (P.chainTopIdx i j) i := by rw [P.chainBotCoeff_sub_chainTopCoeff h]