Thread: Bijection

Give an explicit example of a bijection from [0,1] to the set of real numbers.

I'm confused on how to do this one because it is a closed set.

Recall that a finite composition of bijections is also a bijection. [I don't remember the infinite case]

Let f be a bijection between [0,1] and (0,1) and let g be a bijection between (0,1) and R. then g o f is a bijection between [0,1] and R

f(x): [0, 1] -> (0, 1) by

f(0) = 1/2
If n is a positive integer, then f(1/n) = 1/(n + 2)
Otherwise (that is, if x is not zero and cannot be written in the form 1/n for n a positive integer), then f(x) = x.

g(x) = tan( x - /2)

Originally Posted by lovesmath

Give an explicit example of a bijection from [0,1] to the set of real numbers. I'm confused on how to do this one because it is a closed set.

You should not be confused: the real number set is closed as a topological space.

There is a bijection , this done by shifting a countable set.

is a bijection .

What about a composition of those two?

See also this thread for a bijection between [0, 1] and (0, 1).