Let T= {ti: i exists in N} and S be sets that T is denumerable and there exists a surjection f: T->S. Show that there exists an injection of S->N.
I started off the problems applying the definitions. I must have made a big mistake somewhere because my teacher told me it was nonsense... Also I wrongfully assumed that S was denumerable. It might be possible to prove that it is, but I had just assumed and that was incorrect. Thank you!