Answer to Question #66815 in Abstract Algebra for Pushpa

Question

a) Check whether or not A={z€C*||z|€Q} is a subgroup of
i) (C*, .)
ii) (C ,+)

b) Let (G, .) be a finite abelian group and m€N. Prove that
S={g€G |(o(g),m)=1}<_G