English
There is a full, robust triangulated structure on the Homotopy category of cochain complexes, i.e., it carries a compatible class of distinguished triangles satisfying the axioms.
Русский
Гомотопическая категория комплексoв коchain обладает полной триангулированной структурой, включающей допустимый набор выделенных треугольников, удовлетворяющих аксиомам.
LaTeX
$$$\text{IsTriangulated} \big(\mathrm{HomotopyCategory}(V,c)\big)$$$
Lean4
theorem mappingConeCompTriangleh_distinguished :
(mappingConeCompTriangleh f g) ∈ distTriang (HomotopyCategory C (ComplexShape.up ℤ)) :=
by
refine ⟨_, _, (mappingConeCompTriangle f g).mor₁, ⟨?_⟩⟩
refine
Triangle.isoMk _ _ (Iso.refl _) (Iso.refl _) (isoOfHomotopyEquiv (mappingConeCompHomotopyEquiv f g)) (by cat_disch)
(by simp) ?_
dsimp [mappingConeCompTriangleh]
rw [CategoryTheory.Functor.map_id, comp_id, ← Functor.map_comp_assoc]
congr 2
exact (mappingConeCompHomotopyEquiv_comm₂ f g).symm