Problem:
Find the norm and argument (phase angle in radians) of $\pi  \left(-\cos \left(\frac{\pi }{15}\right)-i \sin \left(\frac{\pi }{15}\right)\right)$.
Answer:
Norm: $\pi  \sqrt{\sin ^2\left(\frac{\pi }{15}\right)+\cos ^2\left(\frac{\pi }{15}\right)}$
Argument: $-\frac{14 \pi }{15}$
{'source': 'AMPS', 'file': 'amps/mathematica/algebra/complex_norm_and_arg/39690.txt'}