Consider the following:

1. ${\cos }^4\theta -{\sin }^4\theta =\frac{2\tan \theta }{1-{\tan }^2\theta },0<\theta <\frac{\pi }{2}$

2. $cosec\theta +\cot \theta =\frac{1}{cosec\theta -\cot \theta },0<\theta <\frac{\pi }{2}$

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?