$\cos 3 x=-1$ হলে $x=?$

$(2 n+1) \frac{\pi}{12}, n \in \mathbb{Z}$

$(2 n+1) \frac{\pi}{6}, n \in \mathbb{Z}$

$(2 \mathrm{n}+1) \frac{\pi}{3}, \mathrm{n} \in \mathbb{Z}$

$(2 \mathrm{n}+1) \pi, \mathrm{n} \in \mathbb{Z}$