theorem th262a:
  F |=0 A implies F |= A
proof
  assume Z1: F |=0 A;
  let M;
  assume
A1: M |= F;
  let i;
  M^\i |=0 F by A1,LTLAXIO1:29,Th1;then
  M^\i |=0 A by Z1;then
  (SAT M).[i+0,A] =1 by LTLAXIO1:28;
  hence (SAT M).[i,A]=1;
end;
