☼ Union of  Sets  :   The union of  two sets  A  and  B, denoted by  A  B is the set of  all those elements which are either in A or in B or in both A and B.

Thus,  A  B  =  { x : x  A  or  x  B }.

Clearly,  x  A  B   x  A  or  x  B.

And, x  A  B   x  A  and  x B.

 e.g. (i) If  A  =  { a, b, c, d } and  B  =  { b, d, e, f }, then

A  B  =  { a, b, c, d, e, f }

(ii) If  A is the set of  all even integers and B is the set of  all odd integers, then clearly, A  B  is the set of  all integers.

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