1. **State the problem:** Prove or simplify the expression $$\frac{\cos(u - v)}{\cos u \sin v} = \tan u + \cot v$$.
2. **Recall the cosine difference formula:**
$$\cos(u - v) = \cos u \cos v + \sin u \sin v$$
3. **Substitute the formula into the left side:**
$$\frac{\cos u \cos v + \sin u \sin v}{\cos u \sin v}$$
4. **Split the fraction into two parts:**
$$\frac{\cos u \cos v}{\cos u \sin v} + \frac{\sin u \sin v}{\cos u \sin v}$$
5. **Simplify each term by canceling common factors:**
$$\frac{\cancel{\cos u} \cos v}{\cancel{\cos u} \sin v} + \frac{\sin u \cancel{\sin v}}{\cos u \cancel{\sin v}} = \frac{\cos v}{\sin v} + \frac{\sin u}{\cos u}$$
6. **Recognize the trigonometric functions:**
$$\frac{\cos v}{\sin v} = \cot v \quad \text{and} \quad \frac{\sin u}{\cos u} = \tan u$$
7. **Rewrite the expression:**
$$\tan u + \cot v$$
**Final answer:**
$$\frac{\cos(u - v)}{\cos u \sin v} = \tan u + \cot v$$
This confirms the given identity.
Cosine Identity 79378C
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