Lean4
/-- Auxiliary definition for `rotateTrianglehIso`. -/
noncomputable def rotateHomotopyEquivComm₂Homotopy :
Homotopy ((triangle φ).mor₃ ≫ (rotateHomotopyEquiv φ).hom) (inr (CochainComplex.mappingCone.inr φ)) :=
(Cochain.equivHomotopy _ _).symm
⟨-(snd φ).comp (inl (inr φ)) (zero_add (-1)), by
ext p
dsimp [rotateHomotopyEquiv]
-- the following list of lemmas has been obtained by doing
-- simp? [ext_from_iff _ _ _ rfl, ext_to_iff _ _ _ rfl,
-- (inl φ).leftShift_v 1 0 (neg_add_cancel 1) p p (add_zero p) (p + 1) (by omega),
-- δ_zero_cochain_comp _ _ _ (neg_add_cancel 1),
-- Cochain.comp_v _ _ (add_neg_cancel 1) p (p + 1) p rfl (by omega),
-- (Cochain.ofHom φ).leftShift_v 1 1 (zero_add 1) p (p + 1) rfl (p + 1) (by omega)]⟩
simp only [Int.reduceNeg, Cochain.ofHom_comp, ofHom_lift, Cocycle.coe_neg, Cocycle.leftShift_coe,
Cocycle.ofHom_coe, Cochain.comp_zero_cochain_v, shiftFunctor_obj_X', Cochain.ofHom_v, δ_neg,
δ_zero_cochain_comp _ _ _ (neg_add_cancel 1), δ_inl, Int.negOnePow_neg, Int.negOnePow_one, δ_snd,
Cochain.neg_comp, Cochain.comp_assoc_of_second_is_zero_cochain, smul_neg, Units.neg_smul, one_smul, neg_neg,
neg_add_rev, Cochain.add_v, Cochain.neg_v, Cochain.comp_v _ _ (add_neg_cancel 1) p (p + 1) p rfl (by cutsat),
Cochain.zero_cochain_comp_v, ext_from_iff _ _ _ rfl, inl_v_triangle_mor₃_f_assoc, triangle_obj₁,
shiftFunctor_obj_X, shiftFunctorObjXIso, HomologicalComplex.XIsoOfEq_rfl, Iso.refl_inv, Preadditive.neg_comp,
id_comp, Preadditive.comp_add, Preadditive.comp_neg, inl_v_fst_v_assoc, inl_v_snd_v_assoc, zero_comp, neg_zero,
add_zero, ext_to_iff _ _ _ rfl, liftCochain_v_fst_v,
(Cochain.ofHom φ).leftShift_v 1 1 (zero_add 1) p (p + 1) rfl (p + 1) (by cutsat), mul_one, sub_self, mul_zero,
Int.zero_ediv, Iso.refl_hom, Preadditive.add_comp, assoc, inl_v_fst_v, comp_id, inr_f_fst_v, comp_zero,
liftCochain_v_snd_v, (inl φ).leftShift_v 1 0 (neg_add_cancel 1) p p (add_zero p) (p + 1) (by cutsat),
Int.negOnePow_zero, inl_v_snd_v, inr_f_snd_v, zero_add, and_self, inr_f_triangle_mor₃_f_assoc,
inr_f_fst_v_assoc, inr_f_snd_v_assoc, neg_add_cancel]⟩