reserve a,b,c for positive Real,
  m,x,y,z for Real,
  n for Nat,
  s,s1,s2,s3,s4,s5 for Real_Sequence;

theorem Th2:
  (a+b)/2>=sqrt(a*b)
proof
  (a+b)/2>=(2*sqrt(a*b))/2 by SIN_COS2:1,XREAL_1:72;
  hence thesis;
end;
