polar Representation of Complex numbers

We may also represent a complex number $c= a+ib$ in polar form. Since $x= r\cos \theta$ and $y = r\sin \theta$ we may write $c= a+ib$ as

$c= r\cos \theta + r i \sin \theta = r( \cos \theta + i \sin \theta ) = r cis \theta$

This representation is very useful when we multiply or divide complex numbers.

for trigonometric representation of complex numbers please see

http://ppatten.ngc.peachnet.edu/trgcomp.htm