theorem
  f = max+f - max-f
proof
  f = max+(R_EAL f)-max-(R_EAL f) by MESFUNC2:23;
  then f = R_EAL(max+f)-max-(R_EAL f) by Th30;
  then f = R_EAL(max+f)-R_EAL(max-f) by Th30;
  then f = R_EAL(max+f - max-f) by Th23;
  hence thesis;
end;
