Cyclicness is invariant under isomorphism

Dependencies:

  1. Isomorphism on Groups
  2. Mapping of power is power of mapping

If $\langle a \rangle \cong H$ via $\phi$, then $H = \langle \phi(a) \rangle$. This means that $H$ is cyclic.

Proof

\begin{align} & g \in \langle \phi(a) \rangle \\ &\iff \exists k, g = \phi(a)^k \\ &\iff \exists k, g = \phi(a^k) \\ &\iff g \in \phi(\langle a \rangle) = H \end{align}

Therefore, $\langle \phi(a) \rangle = H$.

Dependency for:

  1. Zm × Zn is isomorphic to Zmn iff m and n are coprime

Info:

Transitive dependencies:

  1. Group
  2. Homomorphism on groups
  3. Mapping of power is power of mapping
  4. Isomorphism on Groups