English
Alternative formulation of covariant_sequence_exact₁'. The five-term exactness is established via ladder arguments and Ext-hom equivalences.
Русский
Альтернативная формулировка covariant_sequence_exact₁'. Доказано существование точности по лестничным аргументам и эквивалентностям Ext.
LaTeX
$$$(\\mathrm{covariantSequence\\_₁'})(X,hS)\\text{ is exact}$$$
Lean4
theorem covariantSequence_exact : (covariantSequence X hS n₀ n₁ h).Exact :=
exact_of_δ₀ (covariant_sequence_exact₂' X hS n₀).exact_toComposableArrows
(exact_of_δ₀ (covariant_sequence_exact₃' X hS n₀ n₁ h).exact_toComposableArrows
(exact_of_δ₀ (covariant_sequence_exact₁' X hS n₀ n₁ h).exact_toComposableArrows
(covariant_sequence_exact₂' X hS n₁).exact_toComposableArrows))