3 May
2006
3 May
'06
4:32 p.m.
Gene wrote: << A set is finite if there exists no bijection of it onto one of its proper subsets. . . .
Maybe a bit simpler is to say either 1. a set X is finite if there is no surjection s: X -> X u {X}, or 2. a set X is finite if there is no injection i: X u {X} -> X. Exercise: Show 1. <=> 2. --Dan