📝 Sigma Notation

Q1. Compute \(\sum_{k=0}^{3} (-1)^k\).

💡 Difficulty: easy | ✅ Correct: A

Q2. Which expression gives a sigma‑based approximation of \(\pi\) using an inscribed regular \(n\)-gon in a unit circle?

💡 Difficulty: medium | ✅ Correct: B

Q3. In proving \(\lim_{n \to \infty} \frac{n}{2} \sin\left( \frac{2\pi}{n} \right) = \pi\), which step is essential?

💡 Difficulty: hard | ✅ Correct: A