Let G be a group. Show that the mapping phi_a: g-> aga^-1, where a,g are members of G is an automorphism of G. (Inner Automorphism Induced by a)
Just post what you did. This should be a straightforward problem if you go in steps. Step one is to know is homomorphism. Step two is to show is one-to-one. Step three is to show is onto.