If $(\mathbb{Z}, +) \cong (C_\infty, \cdot)$, then does there exists a normal subgroup from $C_\infty$ (call it $K$) such that $K \cong 2\mathbb{Z}$?
I tried the following:
If $q \in C_\infty$, then $\langle q^2 \rangle := \{q^{2k} | k \in \mathbb{Z}\} \le C_\infty$.
Let $\beta: 2\mathbb{Z} \to \langle q^2 \rangle$ such that $\beta (m) = m^2$.
Unfortunately, this is not a homomorphism.
Important to note: This is just a curious question, NOT a homework.
Any hints will help.
EDIT
I think it'll be $\beta (2) = q^2$, where $q \in C_\infty$. Is that correct?