Abstract Algebra/Group Theory/Group/a Cyclic Group of Order n is Isomorphic to Integer Moduluo n with Addition

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Let Cm be a cyclic group of order m generated by g with

Let be the group of integers modulo m with addition

Cm is isomorphic to


Let n be the minimal positive integer such that gn = e

Proof of Lemma
Let i > j. Let i - j = sn + r where 0 ≤ r < n and s,r,n are all integers.

2. as i - j = sn + r, and gn = e

4. as n is the minimal positive integer such that gn = e
and 0 ≤ r < n

5. 0. and 7.


0. Define   
Lemma shows f is well defined (only has one output for each input).
f is homomorphism:
f is injective by lemma
f is surjective as both and have m elements and f is injective