# Thread:

1. ## Bijection

Prove that there is a bijection between (0,1) and (b,infinity) for any real number b.

A function is needed. I've though about the function f(x)=b/x but it won't work if b<=0. Any idea?

2. Originally Posted by TitaniumX
Prove that there is a bijection between (0,1) and (b,infinity) for any real number b.

A function is needed. I've though about the function f(x)=b/x but it won't work if b<=0. Any idea?
How about f(x) = b - 1 + 1/x?

3. Originally Posted by TitaniumX
Prove that there is a bijection between (0,1) and (b,infinity) for any real number b.

A function is needed. I've though about the function f(x)=b/x but it won't work if b<=0. Any idea?
$f (x)= tan(\pi x - \pi/2)$ is (I believe) standard for expanding $(0, 1)$ to $\mathbb{R}$, so I would use this.

This can be relatively easily manipulated to give you the function you want.

(Half it to give you a bijection between $(0, 1)$ and $(0, \infty)$, then scale).
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