Circle Chords E1A192
1. **Problem statement:**
Consider a circle with $n$ points marked on it, where $n \geq 2$. We want to find how many different chords can be drawn by connecting two of these $n$ points.
2. **Formula used:**
The number of chords formed by connecting two points out of $n$ points is the number of combinations of $n$ points taken 2 at a time, which is given by:
$$\binom{n}{2} = \frac{n(n-1)}{2}$$
3. **Explanation:**
- Each chord is uniquely determined by choosing 2 distinct points on the circle.
- Since order does not matter (chord between point A and B is the same as between B and A), we use combinations, not permutations.
4. **Intermediate work:**
- Calculate the number of ways to choose 2 points from $n$ points:
$$\binom{n}{2} = \frac{n!}{2!(n-2)!} = \frac{n(n-1)}{2}$$
5. **Final answer:**
The number of different chords that can be drawn is:
$$\boxed{\frac{n(n-1)}{2}}$$