# Trapping a line with a curve

## Prof. David Epstein, University of Warwick

I will talk about a problem that I have used in the past to motivate undergraduate courses on topology or on metric spaces. In fact I would usually present 6 different problems at the beginning of each course, but I’m only planning to talk to the Oxford Invariants about one of them. What are the features that my problems are required to have?

- Problem instantly comprehensible to everyone in the class. In fact, the problems I will talk about will be comprehensible to virtually everyone, including those who gave up mathematics in despair in their early teens.
- Answer to problem can be guessed (but the intuition may be wrong). For this part, you will NEED A RULER (or be sitting next to someone with a ruler).
- Correct proof of answer requires some non-trivial mathematics. In this case, some topology or metric space theory.