સમીકરણ $\frac{\sin^3 \theta - \cos^3 \theta}{\sin \theta - \cos \theta} - \frac{\cos \theta}{\sqrt{1 + \cot^2 \theta}} - 2 \tan \theta \cot \theta = -1$ ક્યારે સાચું છે?

• A
  $\theta \in \left( 0, \frac{\pi}{2} \right)$
• B
  $\theta \in \left( \frac{\pi}{2}, \pi \right)$
• C
  $\theta \in \left( \pi, \frac{3\pi}{2} \right)$
• D
  $\theta \in \left( \frac{3\pi}{2}, 2\pi \right)$