1. The problem statement, all variables and given/known data let phi : G --->G' be an isomorphism of groups. let x element of G and let x'=phi(x) Prove that the orders of x and x' are equal 3. The attempt at a solution I dont even know what the order of a isomorphism means. As far as i know, an isomorphism is just a bijective map from G to G'. How does this have order?