English
The HasFDerivAtFilter for a product-valued map is equivalent to the family of HasFDerivAtFilter for each coordinate, with the projection composed with Φ'.
Русский
Стандартная эквивалентность для произведения: производная по фильтру коэффициентов равна по всем координатам.
LaTeX
$$$\\HasFDerivAtFilter Φ Φ' x L \\iff ∀ i, HasFDerivAtFilter (fun x => Φ x i) ((proj i).comp Φ') x L.$$$
Lean4
theorem hasFDerivAtFilter_pi :
HasFDerivAtFilter (fun x i => φ i x) (ContinuousLinearMap.pi φ') x L ↔ ∀ i, HasFDerivAtFilter (φ i) (φ' i) x L :=
hasFDerivAtFilter_pi'