Friday, October 30, 2015

real analysis - Finding bijection from (0,1) → N



How exactly do I go about finding a bijection between (0,1) → N \ {0}



so (0,1)(1,). I figured I could look at this as finding a function from (0,1)(0,) and just adding 1.




I've seen examples where f(x) = 1x1 then f(0)= and f(1)=0 (but these were on closed sets)



I couldn't find an example of a function such that lim or \lim_{x\to 0} = \infty which is what it looks like I need here.



Can someone give me an example, or a way to find such a function?


Answer



Here are two bijections f from (0,1) to (1,\infty):



1) Let f(x)=\frac{1}{1-x};




2) Let f(x)=1+\tan\left(\frac{\pi x}{2}\right).


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