问题8：为什么有了同构概念，我们还需 要研究同态？ A homo- morphism between groups (G,)and (H,o)is a map o:G-H such that p(g1·92）=p(g1)o(g2） for g,92EG.The range of o in H is called the homomorphic image of Example 1.Let G be a group and gG.Define a map ZG by o(n)=g".Then o is a group homomorphism,since o(m +n)gmtn g"g"=o(m)o(n). This homomorphism maps Z onto the cyclic subgroup of G generated by g.问题8：为什么有了同构概念，我们还需 要研究同态？