Remember, if you have trouble finding the command for a math symbol you want to use, try googling it, email me, or try looking in this Short Math Guide for $\LaTeX{}$.
Suppose that $\phi:G_1 \rightarrow G_2$ is an isomorphism from the group $(G_1,*)$ to the group $(G_2,\odot)$. Prove that $\phi(g^{-1}) = [\phi(g)]^{-1}$. (See Theorem 3.54.)
Suppose that $\phi:G_1 \rightarrow G_2$ is an isomorphism from the group $(G_1,*)$ to the group $(G_2,\odot)$. Prove that if $G_1$ is abelian, then $G_2$ is abelian. (See Theorem 3.64.)