
theorem Th1:
  for a being Element of G_Real holds ex b being Element of G_Real st b + b = a
proof
  set G = G_Real;
  let a be Element of G;
  reconsider a as Element of REAL;
  reconsider b9 = a/2 as Element of REAL by XREAL_0:def 1;
  consider b being Element of G such that
A1: b = b9;
  b + b = a by A1;
  hence thesis;
end;
