English
For every integer n, the composition of S_R(n) with the polynomial 2X equals U_R(n): (S_R(n)).comp(2 X) = U_R(n).
Русский
Для каждого целого n: композиция S_R(n) с 2X дает U_R(n): (S_R(n)).comp(2 X) = U_R(n).
LaTeX
$$$ (S_R(n)).\circ(2 X) = U_R(n) $$$
Lean4
theorem S_comp_two_mul_X (n : ℤ) : (S R n).comp (2 * X) = U R n := by
induction n using Polynomial.Chebyshev.induct with
| zero => simp
| one => simp
| add_two n ih1 ih2 => simp_rw [U_add_two, S_add_two, sub_comp, mul_comp, X_comp, ih1, ih2]
| neg_add_one n ih1 ih2 => simp_rw [U_sub_one, S_sub_one, sub_comp, mul_comp, X_comp, ih1, ih2]