Let $f:\mathbb{C}\rightarrow \mathbb{C}$ be an analytic function. Pick out the statements for which $f$ is not necessarily constant.
$\operatorname{Im}(f'(z))>0$ for all $z\in \mathbb{C}$
$f(n)=3$ for all $n\in \mathbb{Z}$
- $f'(0)=0$ and $|f'(z)|\leq 3$ for all $z\in \mathbb{C}$
My attempt: For (1) $f(z)=iz$ is a function which satisfies (1) but is not constant.
For (2) $f(z)=3+\sin(n\pi z)$ is also a non-constant function satisfying (2)
For (3), $f$ is entire implies $f'$ is entire. It is given that $f'$ is bounded hence $f'$ is constant but then $f'(0)=0$. Therefore, $f'=0$ and therefore $f$ is constant.
- Are my attempts correct?