Cotangent Discontinuity
1. **Problem statement:** Sketch the function $f(x) = \cot(x)$ and mark its points of discontinuity.
2. **Formula and definition:** The cotangent function is defined as $\cot(x) = \frac{\cos(x)}{\sin(x)}$.
3. **Important rules:**
- $\cot(x)$ is undefined where $\sin(x) = 0$ because division by zero is undefined.
- The sine function is zero at $x = k\pi$ for all integers $k$.
4. **Points of discontinuity:**
- Therefore, $f(x)$ has vertical asymptotes (discontinuities) at $x = k\pi$, where $k$ is any integer.
5. **Behavior between discontinuities:**
- Between these points, $\cot(x)$ is continuous and decreases from $+\infty$ to $-\infty$.
6. **Summary:**
- The graph of $f(x) = \cot(x)$ has vertical asymptotes at $x = k\pi$.
- It is periodic with period $\pi$.
Final answer: The function $f(x) = \cot(x)$ is discontinuous at $x = k\pi$ for all integers $k$ and continuous elsewhere.