A group with a trivial automorphism group

Let G be a group and suppose Aut(G) is trivial.

  1. Show that G is abelian.
  2. Show that for any abelian group H, the inversion map ϕ(h)=h1 is an automorphism.
  3. Use parts (1) and (2) above to show that g2 is the identity element for every gG.