1. **State the problem:** Solve the equation $$\csc\theta - 1 = \frac{\cot^2\theta}{\csc\theta + 1}$$ for $\theta$.
2. **Recall identities:**
- $\csc\theta = \frac{1}{\sin\theta}$
- $\cot\theta = \frac{\cos\theta}{\sin\theta}$
- $\cot^2\theta = \csc^2\theta - 1$
3. **Rewrite the right side using the identity:**
$$\frac{\cot^2\theta}{\csc\theta + 1} = \frac{\csc^2\theta - 1}{\csc\theta + 1}$$
4. **Factor numerator as difference of squares:**
$$\csc^2\theta - 1 = (\csc\theta - 1)(\csc\theta + 1)$$
5. **Substitute back:**
$$\frac{(\csc\theta - 1)(\csc\theta + 1)}{\csc\theta + 1}$$
6. **Cancel common factor $\csc\theta + 1$ (assuming $\csc\theta \neq -1$):**
$$\frac{\cancel{(\csc\theta - 1)}\cancel{(\csc\theta + 1)}}{\cancel{\csc\theta + 1}} = \csc\theta - 1$$
7. **Now the equation becomes:**
$$\csc\theta - 1 = \csc\theta - 1$$
8. **This is an identity true for all $\theta$ where the original expression is defined, except where $\csc\theta + 1 = 0$, i.e., $\csc\theta = -1$.**
9. **Find where $\csc\theta = -1$: since $\csc\theta = \frac{1}{\sin\theta}$, this means $\sin\theta = -1$.**
10. **$\sin\theta = -1$ at $\theta = \frac{3\pi}{2} + 2k\pi$, $k \in \mathbb{Z}$. These values are excluded because they make the denominator zero.**
**Final answer:** The equation holds for all $\theta$ except $\theta = \frac{3\pi}{2} + 2k\pi$, $k \in \mathbb{Z}$.
Trig Identity 429B2D
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