$\cos \theta=\frac{1}{\sqrt{2}}$ হলে $\boldsymbol{\theta}=$ কত ?

$2 n \pi+\frac{\pi}{4} ; n \in \mathbb{Z}$

$2 n \pi \pm \frac{\pi}{4}, n \in \mathbb{Z}$

$2 n \pi-\frac{\pi}{4}, n \in \mathbb{Z}$

$n \pi \pm \frac{\pi}{4} ; n \in \mathbb{Z}$