Mathematics

Problem

The principal value of

\arg(z)

, where

z = \left(1 + \cos \frac{8\pi}{5}\right) + i \sin \frac{8\pi}{5}

(where,

i = \sqrt{-1}

) is given by a.

-\frac{\pi}{5}

-\frac{4\pi}{5}

\frac{\pi}{5}

\frac{4\pi}{5}