You need to show that these are the only automorphisms of . Use the fact that automorphisms map generators to generators. Now, what are the generators of ?
This one is mostly a problem with the definitions, I think.
I am asked to prove that is isomorphic to , where is the group of all automorphisms of .
Obviously the identity function is in . The only other automorphism I can come up with is . etc, etc. to finish showing the isomorphism between and .
Are there truly only two members in ? It seems there should be more, but I can't find any.