reserve r,r1,r2, s,x for Real,
  i for Integer;

theorem Th36:
  PI < r & r <= 2*PI implies cos r > -1
proof
  assume
A1: PI < r & r <= 2*PI;
  cos r >= -1 by Th5;
  hence thesis by A1,Th29,XXREAL_0:1;
end;
