Euler Path Circuit
1. **Problem Statement:** Determine if the given graph has (i) an Euler's path and (ii) an Euler's circuit.
2. **Recall Definitions:**
- An **Euler's path** is a trail in a graph that visits every edge exactly once.
- An **Euler's circuit** is an Euler's path that starts and ends on the same vertex.
3. **Key Theorems:**
- A connected graph has an Euler's circuit if and only if every vertex has an even degree.
- A connected graph has an Euler's path (but not an Euler's circuit) if and only if exactly two vertices have odd degree.
4. **Analyze Vertex Degrees:**
- Vertex 1 connects to 2 and 3 → degree 2 (even)
- Vertex 2 connects to 1 and 3 → degree 2 (even)
- Vertex 3 connects to 1, 2, 4, 6 → degree 4 (even)
- Vertex 4 connects to 3 and 5 → degree 2 (even)
- Vertex 5 connects to 4 and 6 → degree 2 (even)
- Vertex 6 connects to 3, 5, 7 → degree 3 (odd)
- Vertex 7 connects to 6 → degree 1 (odd)
5. **Count Odd Degree Vertices:**
- Odd degree vertices are 6 and 7 (2 vertices).
6. **Conclusion:**
- Since exactly two vertices have odd degree, the graph has an Euler's path but does not have an Euler's circuit.
**Final answer:**
- (i) Euler's path: Yes, because exactly two vertices have odd degree.
- (ii) Euler's circuit: No, because not all vertices have even degree.