Definition:Polar Form of Complex Number/Also known as

Polar Form of Complex Number: Also known as
Some sources refer to polar form as trigonometric form.

As $\cos \theta + i \sin \theta$ appears so often in complex analysis, the abbreviation $\cis \theta$ is frequently seen.

Hence $r \paren {\cos \theta + i \sin \theta}$ can be expressed in the economical form $r \cis \theta$.