Let k be a positive integer.(adsbygoogle = window.adsbygoogle || []).push({});

define G_k = {x| 1<= x <= k with gcd(x,k)=1}

prove that:

a)G_k is a group under multiplication modulos k (i can do that).

b)G_nm = G_n x G_m be defining an isomorphism.

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# Direct product

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