English
Let L be a localization; the distinguished triangles in the image essImageDistTriang(D) are exactly those triangles in D that come from distinguished triangles in C via L.
Русский
Пусть L — локализация; разностного треугольники в образе essImageDistTriang(D) — это ровно те треугольники в D, которые происходят из distinguished triangles в C через L.
LaTeX
$$$T \in L.essImageDistTriang \quad\text{iff}\quad \exists\; T'\in distTriang(C),\; T \cong L.mapTriangle.obj T'$$$
Lean4
/-- Given a functor `C ⥤ D` from a pretriangulated category, this is the set of
triangles in `D` that are in the essential image of distinguished triangles of `C`. -/
def essImageDistTriang : Set (Triangle D) := fun T =>
∃ (T' : Triangle C) (_ : T ≅ L.mapTriangle.obj T'), T' ∈ distTriang C