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In this paper we define the concepts of a "strict morphism" as a suitable map between geometric spaces (as a generalization of hyperstructures), and its kernel. Then we introduce the concepts of a "quotient geometric space", an "exact sequence", an "exact hypersequence", a "homology" and a "hyperhomology" of geometric spaces. Finally we generalize some famous theorems from groups and modules in this direction, such as the "isomorphism theorem", the "five short lemma", the "snake lemma", the "exact triangle", etc., by some conditions that are naturally valid for groups. [ABSTRACT FROM AUTHOR]

In this paper, we study an excision theorem of the dihedral and reflexive (co)homology theory of associative algebras. That is, for such an extension, we obtain a six-term exact sequence in the dihedral cohomology. Also, we present and prove the relation between cyclic and dihedral cohomology of algebras and some examples. [ABSTRACT FROM AUTHOR]