Let X be a non-empty set. Define the set Z to be the collection of all subsets of X. Consider the binary operation “union” in the set Z, that is, for A and B that are subsets of X, let
A*B=A∪B
Determine which of the properties of the binary operation is/are satisfied in Z under *.
Let G=D_8, and let N={e,a^2,a^4,a^6}.
(a) Find all left cosets and all right cosets of N, and verify that N is a normal subgroup of G.
(b) Show that G/N has order 4, but is not cyclic.
Show that if g is a non cyclic group of order n then g has no elements of order n. Further give an example with justification of a non cyclic group all of whose proper subgroups are cyclic