46.
Consider the following:
1. \( \cos^{4} \theta - \sin^{4} \theta = \frac{2 \tan \theta}{1 - \tan^{2} \theta}, 0 < \theta < \frac{\pi}{2} \)
2. \( \mathrm{cosec} \theta + \cot \theta = \frac{1}{\mathrm{cosec} \theta - \cot \theta}, 0 < \theta < \frac{\pi}{2} \)
3. \( \cos^{2} \theta - \sin^{2} \theta = \frac{1 - \tan^{2} \theta}{1 + \tan^{2} \theta}, 0 < \theta < \frac{\pi}{2} \)
Which of the above equations are identities?