1.3.10 Theorem The following statements are equivalent:\ (a)

S

is a countable set.\ (b) There exists a surjection of

N

onto

S.1H;S->N

.\ (c) There exists an injection of

S

into

N

.

H_(2):N->S

1.3.10 Theorem The following statements are equivalent: (a) S is a countable set. (b) There exists a surjection of N onto S.1H1;SN (c) There exists an injection of S into N. H2:NS