Topology: Lecture 4: definition of topology, basis of topology, closed sets and examples

[audxc]

I am upset that the 'topologize ' joke got me to chuckle

At 14:20 any open subset that is bounded has least upper bound so either an arbitrary union gives you an open interval with Max{a_i} as the upper bound or the whole line.

At 17:00 I think a picture helps with the proof, and y our notation got in your way, but I see you got it.

At 43:00 Would the Z.T. give you a non-simply connected topological space?

[DB-nlxw]

can you solve some exercises step by step. thanks.