# Math Help - complex numbers in polar form

1. ## complex numbers in polar form

if z=5i and w=(-9*sqrt(2))/2 + (9*sqrt(2))/2

determine z/w in polar form

Could some one please get me started I dont know how you can find the angle formed when z=5i?
dont I need a real part not just imaginary

Thanks

2. Hello,

Originally Posted by samdmansam
if z=5i and w=(-9*sqrt(2))/2 + (9*sqrt(2))/2
Isn't it w=(-9*sqrt(2))/2 + (9*sqrt(2))/2 i ?

determine z/w in polar form
First of all, multiply above and below by the conjugate of w

Could some one please get me started I dont know how you can find the angle formed when z=5i?
I think this would come later
Try to get to the step I mentioned.

dont I need a real part not just imaginary
If you have z=5i, it means that z=0+5i

$|z|=5$

$5i=5(\cos(\theta)+i \sin(\theta)$

So we can see that $\cos(\theta)=0$ and $\sin(\theta)=1$

3. there is a similar question asked previously have a look:
http://www.mathhelpforum.com/math-he...-form-c-n.html

4. ## thanks but need a bit more help

I got (5/9)cis(11/6*pi)
but the answer needs to be between (-pi,pi]?
dont really understand that