Find the smallest integer n for which (1+i/1-i)^n=1
Hmm I don't know any reference in English.
I used this formula :
$\displaystyle a+ib=\sqrt{a^2+b^2} \cdot e^{i \arctan \frac ab}$
then use the properties of i :
$\displaystyle i^2=-1$
then $\displaystyle i^4=1$
etc..
http://en.wikipedia.org/wiki/Complex...the_polar_form