    Sentence 1:> If. aiand ¢  are coprinie, °<°.which.  theorem ‘holds’; that: .an  arithmetic. progression  has: van infinite’ numbér  of. primes?    Sentence | 2: TF this  necessary . condition: is  Satisfied, Dirichlet''s.  theorem... or) arithmetic    progressions..: asserts  that. the. progression  contains infinitely    many: primes...