how to finish this question?
Express z=3-4i in the polar form.
the polar form of a complex number $\displaystyle a + ib$ is given by $\displaystyle re^{i \theta}$
where $\displaystyle r = |a + ib| = \sqrt{a^2 + b^2}$
and $\displaystyle \theta = \arctan \frac ba$
and we measure $\displaystyle \theta$ using positive angle measured from the positive real axis.