theorem Th24:
  |- f^<*p*> & |- f^<*p*>^<*q*> implies |- f^<*q*>
proof
A1: 1 <= len (f^<*p*>) by CALCUL_1:10;
  assume |- f^<*p*> & |- f^<*p*>^<*q*>;
  then |- Ant(f^<*p*>)^<*q*> by A1,CALCUL_1:45;
  hence thesis by CALCUL_1:5;
end;
