What are the polar coordinates of (1 sqrt3)?

I found: ##(2pi/3)##
Consider the following diagram:

We can see that the relationships between rectangular and are:
##r=sqrt(x^2+y^2)##
##theta=arctan(y/x)##
and:
##x=rcos(theta)##
##y=rsin(theta)##
In your case:
##x=1##
##y=sqrt(3)##
use them into:
##r=sqrt(x^2+y^2)##
##theta=arctan(y/x)##
to get:
##r=sqrt(1+3)=sqrt(4)=2##
##theta=arctan(sqrt(3))=60^@=pi/3rad##