Proving Isomorphism of Z4 / (2Z4) and Z2

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SUMMARY

The factor group Z4 / (2Z4) is isomorphic to Z2, as established in the discussion. The quotient group exists because 2Z4 is a normal subgroup of Z4, which is abelian. To prove the isomorphism, one must list the cosets of Z4/2Z4 and demonstrate that the mapping satisfies the properties of an isomorphism. The group Z4/2Z4 contains two elements, confirming its isomorphism to Z2.

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Homework Statement


Why does it make sense (when considering Z4)to form the factor group

Z4 / (2Z4) where kZn = {0, k mod n, 2k mod n, ..., nk mod n}?

I believe that this above factor group is isomorphic to Z2, but how can I prove this?
 
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The quotient group exists because 2Z4 is a normal subgroup of Z4 (since Z4 is abelian, all its subgroups are normal). To show that it is isomorphic to Z2, list the elements of Z4/2Z4 (which are cosets), and write down the isomorphism. Then, prove what you have is indeed an isomorphism, i.e. that it has the properties of an isomorphism.
 
How many elements are in Z4/2Z4? How many groups have that many elements?
 

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