English
For 𝕜 and 𝕝 nontrivially normed fields, with a normed algebra structure, the inverse function x ↦ (1−x)^{-1} has a power-series expansion on the ball of radius 1 around 0.
Русский
Для ненулевых нормированных полей 𝕜 и 𝕝 с нормированной алгеброй обратная функция x ↦ (1−x)^{-1} имеет разложение в ряд степенной на шаре радиуса 1 вокруг 0.
LaTeX
$$HasFPowerSeriesOnBall (fun x : A ↦ (1 - x)^{-1}) (formalMultilinearSeries_geometric 𝕜 A) 0 1$$
Lean4
theorem hasFPowerSeriesOnBall_inv_one_sub (𝕜 𝕝 : Type*) [NontriviallyNormedField 𝕜] [NontriviallyNormedField 𝕝]
[NormedAlgebra 𝕜 𝕝] : HasFPowerSeriesOnBall (fun x : 𝕝 ↦ (1 - x)⁻¹) (formalMultilinearSeries_geometric 𝕜 𝕝) 0 1 :=
by
convert hasFPowerSeriesOnBall_inverse_one_sub 𝕜 𝕝
exact Ring.inverse_eq_inv'.symm