reserve x,y,t for Real;

theorem Th8:
  x>=1 implies sqrt((x+1)/2)>=1
proof
  assume x>=1;
  then x+1>=1+1 by XREAL_1:6;
  then (x+1)/2>=1 by XREAL_1:181;
  hence thesis by SQUARE_1:18,26;
end;
