Definition:Complex Number/Polar Form/Exponential Form

Definition
Let $z := \left \langle {r, \theta} \right \rangle$ be a complex number in polar form. From Euler's Theorem:
 * $e^{i \theta} = \cos \theta + i \sin \theta$

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.