Polar Form of Complex Number/Examples/1 - 2i

Example of Polar Form of Complex Number
The complex number $1 - 2 i$ can be expressed as a complex number in polar form as $\polar {\sqrt 5, -\arctan 2}$.

Proof
Then:

Hence:
 * $\map \arg {1 - 2 i} = \map \arctan {-2} = -\arctan 2$

as $1 - 2 i$ is in Quadrant II.