There are two sets:

- A set: is the points of a disk (of radius 1), so x^2+y^2<1

- B set is: RxR

We should prove that two sets have the same cardinality, so we should find a bijection from A to B.

Thanks for helping me!

- Sep 26th 2010, 07:36 AMdougBijective matching between the points of a disk and the points in the plain
There are two sets:

- A set: is the points of a disk (of radius 1), so x^2+y^2<1

- B set is: RxR

We should prove that two sets have the same cardinality, so we should find a bijection from A to B.

Thanks for helping me! - Sep 26th 2010, 08:49 AMHappyJoe
You can take the following function , where is the open unit disc:

where is a point of , and where is the norm of the point, i.e.