English
The differential commutes with diagonalSuccIsoFree in the sense that d commutes with the inverse of the diagonalSuccIsoFree isomorphism.
Русский
Дифференциал коммутирует с диагональным переходом через диагональный переход, сопряжённый с обратной диагональной изоморфией.
LaTeX
$$$d\\;\\circ\\; (\\mathrm{diagonalSuccIsoFree})^{-1} = (\\mathrm{diagonalSuccIsoFree})^{-1} \\circ (\\text{standardComplex}.d)$$$
Lean4
theorem d_comp_diagonalSuccIsoFree_inv_eq :
d k G n ≫ (diagonalSuccIsoFree k G n).inv =
(diagonalSuccIsoFree k G (n + 1)).inv ≫ (standardComplex k G).d (n + 1) n :=
free_ext _ _ fun i => by
simpa [diagonalSuccIsoFree_inv_hom_single_single (k := k), d_single (k := k), standardComplex.d_eq,
standardComplex.d_of (k := k) (Fin.partialProd i), Fin.sum_univ_succ, Fin.partialProd_contractNth] using
congr(single $(by ext j; exact (Fin.partialProd_succ' i j).symm) 1)