Verify Identity
1. **State the problem:** Verify the trigonometric identity:
$$\frac{1 + \sin \theta}{\cos \theta} + \frac{\cos \theta}{1 + \sin \theta} = 2 \sec \theta$$
2. **Recall important formulas and rules:**
- $\sec \theta = \frac{1}{\cos \theta}$
- Pythagorean identity: $\sin^2 \theta + \cos^2 \theta = 1$
- To verify an identity, simplify one side to see if it equals the other.
3. **Start with the left-hand side (LHS):**
$$\frac{1 + \sin \theta}{\cos \theta} + \frac{\cos \theta}{1 + \sin \theta}$$
4. **Find a common denominator:**
The common denominator is $\cos \theta (1 + \sin \theta)$.
Rewrite each term:
$$\frac{(1 + \sin \theta)^2}{\cos \theta (1 + \sin \theta)} + \frac{\cos^2 \theta}{\cos \theta (1 + \sin \theta)}$$
5. **Combine the fractions:**
$$\frac{(1 + \sin \theta)^2 + \cos^2 \theta}{\cos \theta (1 + \sin \theta)}$$
6. **Expand numerator:**
$$(1 + \sin \theta)^2 = 1 + 2 \sin \theta + \sin^2 \theta$$
So numerator becomes:
$$1 + 2 \sin \theta + \sin^2 \theta + \cos^2 \theta$$
7. **Use Pythagorean identity:**
Replace $\sin^2 \theta + \cos^2 \theta$ with 1:
$$1 + 2 \sin \theta + 1 = 2 + 2 \sin \theta$$
8. **Simplify numerator:**
$$2 + 2 \sin \theta = 2(1 + \sin \theta)$$
9. **Substitute back into fraction:**
$$\frac{2(1 + \sin \theta)}{\cos \theta (1 + \sin \theta)}$$
10. **Cancel common factor $(1 + \sin \theta)$:**
$$\frac{2}{\cos \theta}$$
11. **Rewrite using $\sec \theta$:**
$$2 \sec \theta$$
12. **Conclusion:**
LHS simplifies to RHS, so the identity is verified:
$$\frac{1 + \sin \theta}{\cos \theta} + \frac{\cos \theta}{1 + \sin \theta} = 2 \sec \theta$$