2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/100874By Rickard's work, two rings are derived equivalent if there is a tilting complex, constructed from projective modules over the first ring such that the second ring is the endomorphism ring of this tilting complex. In this work I describe, under some conditions, the homomorphism space in the derived category between two complexes as iterated pull-back of homomorphism spaces between the homologies of the complexes.26 pages, minor changesRings and AlgebrasRepresentation Theory18E30, 16G30text