2. Let X be a topological space. Then the empty set and X are sets that are both open and closed!
Open and Closed Sets have got nothing to do with the day-to-day open and closed.
'And fun? If maths is fun, then getting a tooth extraction is fun. A viral infection is fun. Rabies shots are fun.'
'God exists because Mathematics is consistent, and the devil exists because we cannot prove it'
'But our love is like the wind. I can't see it but I can feel it.' -A Walk to remember