Tan Cot Identity
1. **State the problem:** Prove the trigonometric identity $$\tan \theta + \cot \theta \equiv \frac{2}{\sin 2\theta}$$.
2. **Recall definitions:**
- $$\tan \theta = \frac{\sin \theta}{\cos \theta}$$
- $$\cot \theta = \frac{\cos \theta}{\sin \theta}$$
- Double angle formula: $$\sin 2\theta = 2 \sin \theta \cos \theta$$
3. **Start with the left-hand side (LHS):**
$$\tan \theta + \cot \theta = \frac{\sin \theta}{\cos \theta} + \frac{\cos \theta}{\sin \theta}$$
4. **Find common denominator and combine:**
$$= \frac{\sin^2 \theta}{\sin \theta \cos \theta} + \frac{\cos^2 \theta}{\sin \theta \cos \theta} = \frac{\sin^2 \theta + \cos^2 \theta}{\sin \theta \cos \theta}$$
5. **Use Pythagorean identity:**
$$\sin^2 \theta + \cos^2 \theta = 1$$
6. **Simplify numerator:**
$$= \frac{1}{\sin \theta \cos \theta}$$
7. **Express denominator using double angle formula:**
Since $$\sin 2\theta = 2 \sin \theta \cos \theta$$, then
$$\sin \theta \cos \theta = \frac{\sin 2\theta}{2}$$
8. **Substitute back:**
$$\frac{1}{\sin \theta \cos \theta} = \frac{1}{\frac{\sin 2\theta}{2}} = \frac{2}{\sin 2\theta}$$
9. **Conclusion:**
$$\tan \theta + \cot \theta = \frac{2}{\sin 2\theta}$$, which proves the identity.
**Final answer:** $$\boxed{\tan \theta + \cot \theta \equiv \frac{2}{\sin 2\theta}}$$