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Show that all automorphisms of a group G form a group under function composition.
Then show that the inner automorphisms of G, defined by f : G--->G so that
f(x) = (a^(-1))(x)(a), form a normal subgroup of the group of all automorphisms.

For the first part, I can see that we need to show that f(g(x)) = g(f(x)) for x in G and
use f(x)=x as the identity in the group, but I' not certain how to proceed to show all innG
form a normal subgroup?

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Solution Preview

First part: Let Aut(G) be the set of all automorphisms of a group G.
To show that Aut(G) is a group under function composition, we need to
verify the following three facts.
(1) id(x)=x is the identity of Aut(G). Because for any f in Aut(G) and
any x in G, we have id(f(x))=f(x)=f(id(x)). So ...

Solution Summary

Group automorphisms are investigated. The solution is detailed and well presented. The response received a rating of "5/5" from the student who originally posted the question.