Take the 2-minute tour ×
Mathematics Stack Exchange is a question and answer site for people studying math at any level and professionals in related fields. It's 100% free, no registration required.

I came across the following problem that says:

Consider the functions $f,g\colon \mathbb C \rightarrow \mathbb C$ defined by $f(z)=e^z, g(z)=e^{iz}$. Let $S=\{z \in \mathbb C:Re(z)\in [-\pi,\pi]\}.$ Then which of the following options is correct?

$1$. $f$ is an onto entire function

$2$. $g$ is a bounded function on $\mathbb C$

$3$. $f$ is bounded on $S$

$4$. $g$ is bounded on $S$

Can someone point me in the right direction? Thanks in advance for your time.

share|improve this question
What does $[-z, z]$ mean? –  Michael Albanese Feb 3 '13 at 3:12
I'm sure that you meant something else than $[-z,z]$, since $S$ makes no sense as it is. –  Cameron Buie Feb 3 '13 at 3:36
sorry for the mistake. I have edited it. –  user52976 Feb 3 '13 at 3:41
Thanks for remarking that point +1 –  Babak S. Feb 4 '13 at 17:25

1 Answer 1

up vote 2 down vote accepted

For the first statement, can you find $z \in \mathbb{C}$ such that $f(z) = 0$? For the rest, use the fact that $$|e^z| = |e^{a+bi}| = |e^ae^{bi}| = |e^a||e^{bi}| = |e^a| = e^a = e^{\Re(z)}.$$

share|improve this answer
Thanks a lot sir.I have got it. –  user52976 Feb 3 '13 at 4:18
$f$ is bounded only –  El Angel Exterminador May 3 '13 at 6:43

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.