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Mr Example.

Name: Anonymous 2007-08-30 13:43 ID:eUFPtE+p

I enjoyed those two Monsieur Ejemplé threads so I thought I'd pose a maths question of my own, in fact I'll do two on countability. They're not that hard, but I think they're more enjoyable than calculus

1. Let f : R -> R be monotonic.
Is  the set { x | f is discontinous at x} countable?
where x is in R.


2. A function f : N -> N is increaing if f(n)>= f(n+1)   (if it's bigger than OR equal to) and a decreasing function is similarly defined.

is the set {f | f is increasing} countable?
is the set {f | f is decreasing} countable?

Name: Anonymous 2007-08-31 8:25 ID:lhrjZT0z

They weren't hard, but countabilities just more fun than calculus :p

Ok, this one's slightly harder, but I think the solution's interesting.

Can an uncountably infinite collection of "figures of eight" be placed on RxR such that no two overlap?

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