Search All of the Math Forum:
Views expressed in these public forums are not endorsed by
NCTM or The Math Forum.


quasi
Posts:
12,012
Registered:
7/15/05


Re: Onto [0,1]
Posted:
Apr 25, 2013 5:54 AM


Butch Malahide wrote: >quasi wrote: >> >> If X,Y are subsets of R, and f: X > Y is a monotonic function, >> then f is continuous (with respect to the relative topologies >> on X and Y inherited from R). > >Hmm. Suppose X = [0,1] and Y = [0,1) union {2}. Let f: X > Y >be an orderpreserving bijection, e.g., f(x) = x for x in [0,1), >f(1) = 2. I don't believe that f is continuous with respect to >the relative topologies on X and Y inherited from R. For one >thing, X is compact and connected, while Y is neither. (I guess >that was two things.) I guess you left out some assumptions.
Yes, I realized as much myself.
In fact, the immediate counterexample that ocurred to me was very similar to the one you gave above.
All in all, my claim was pretty silly.
quasi



