\begin{definition}[Definition:Complex Number/Polar Form/Exponential Form]
Let $z := \polar {r, \theta}$ be a complex number in polar form.
From Euler's Formula:
:$e^{i \theta} = \cos \theta + i \sin \theta$
so $z$ can also be written in the form:
:$z = r e^{i \theta}$
This form of presentation of a complex number is known as '''exponential form'''.
\end{definition}