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Mathlib.Algebra.Homology.HomotopyCategory.Triangulated

The triangulated structure on the homotopy category of complexes

In this file, we show that for any additive category C, the pretriangulated category HomotopyCategory C (ComplexShape.up ℤ) is triangulated.

Given two composable morphisms f : X₁ ⟶ X₂ and g : X₂ ⟶ X₃ in the category of cochain complexes, this is the canonical triangle mappingCone f ⟶ mappingCone (f ≫ g) ⟶ mappingCone g ⟶ (mappingCone f)⟦1⟧.

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    Given two composable morphisms f : X₁ ⟶ X₂ and g : X₂ ⟶ X₃ in the category of cochain complexes, this is the canonical triangle mappingCone f ⟶ mappingCone (f ≫ g) ⟶ mappingCone g ⟶ (mappingCone f)⟦1⟧ in the homotopy category. It is a distinguished triangle, see HomotopyCategory.mappingConeCompTriangleh_distinguished.

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      Given two composable morphisms f and g in the category of cochain complexes, this is the canonical morphism (which is an homotopy equivalence) from mappingCone g to the mapping cone of the morphism mappingCone f ⟶ mappingCone (f ≫ g).

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        Given two composable morphisms f and g in the category of cochain complexes, this is the canonical morphism (which is an homotopy equivalence) from the mapping cone of the morphism mappingCone f ⟶ mappingCone (f ≫ g) to mappingCone g.

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          Given two composable morphisms f and g in the category of cochain complexes, this is the homotopyInvHomId field of the homotopy equivalence mappingConeCompHomotopyEquiv f g between mappingCone g and the mapping cone of the morphism mappingCone f ⟶ mappingCone (f ≫ g).

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            Given two composable morphisms f and g in the category of cochain complexes, this is the homotopy equivalence mappingConeCompHomotopyEquiv f g between mappingCone g and the mapping cone of the morphism mappingCone f ⟶ mappingCone (f ≫ g).

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