English
For τ and P, the app of the preimage under whiskeringLeft equals F.map P.decompId_i ≫ τ.app P.X ≫ G.map P.decompId_p.
Русский
Для τ и P, значение на приложении предварительного образа под whiskeringLeft равно F.map P.decompId_i ≫ τ.app P.X ≫ G.map P.decompId_p.
LaTeX
$$whiskeringLeft_obj_preimage_app {F G : Karoubi C ⥤ D} (τ : toKaroubi _ ⋙ F ⟶ toKaroubi _ ⋙ G) (P : Karoubi C) :\n (((whiskeringLeft _ _ _).obj (toKaroubi _)).preimage τ).app P =\n F.map P.decompId_i ≫ τ.app P.X ≫ G.map P.decompId_p$$
Lean4
theorem whiskeringLeft_obj_preimage_app {F G : Karoubi C ⥤ D} (τ : toKaroubi _ ⋙ F ⟶ toKaroubi _ ⋙ G) (P : Karoubi C) :
(((whiskeringLeft _ _ _).obj (toKaroubi _)).preimage τ).app P =
F.map P.decompId_i ≫ τ.app P.X ≫ G.map P.decompId_p :=
by
rw [natTrans_eq]
congr 2
rw [← congr_app (((whiskeringLeft _ _ _).obj (toKaroubi _)).map_preimage τ) P.X]
dsimp
congr