What is the principal argument of z=sin(π7)−icos(π7)z = \sin\left(\frac{\pi}{7}\right) - i\cos\left(\frac{\pi}{7}\right)z=sin(7π)−icos(7π)?
−5π14-\frac{5\pi}{14}−145π
−9π14-\frac{9\pi}{14}−149π
13π14\frac{13\pi}{14}1413π
−π7-\frac{\pi}{7}−7π