यदि $\cos 2x = (\sqrt{2} + 1) \left(\cos x - \frac{1}{\sqrt{2}}\right)$ और $\cos x \neq \frac{1}{\sqrt{2}}$ है,तो $x \in$

• A
  $\left\{2n\pi \pm \frac{\pi}{3} : n \in Z\right\}$
• B
  $\left\{2n\pi \pm \frac{\pi}{6} : n \in Z\right\}$
• C
  $\left\{2n\pi \pm \frac{\pi}{2} : n \in Z\right\}$
• D
  $\left\{2n\pi \pm \frac{\pi}{4} : n \in Z\right\}$