How to calculate this complex number expression How do I calculate this term?
$|(\frac{\sqrt{3}}{2}-\frac{1}{2}i)^{15}|$
I've started by transforming in into polar form:
$|{e^{i(\frac{11}{6}\pi)}}^{15}|$
How do I go on from here?

As @5xum stated, your calculation method is inefficient. However, it is still a valid way to do so. 
Continuing from your progress, I think you meant 
$$|{e^{i(\frac{11}{6}\pi)\cdot 15}}|=|{e^{i(\frac{55}{2}\pi)}}|=^*|{e^{-i(\frac{\pi}{2})}}|=|-i|=?$$
where $(*)$ follows from the fact that $e^{i\theta}$ is $2\pi-$periodic.
