theorem
  for f being non empty constant complex-valued Function ex r being
  Complex st for x being object st x in dom f holds f.x = r
proof
  let f be non empty constant complex-valued Function;
  consider r being object such that
A1: for x being object st x in dom f holds f.x = r by FUNCOP_1:78;
  consider x being object such that
A2: x in dom f by XBOOLE_0:def 1;
  r = f.x by A1,A2;
  hence thesis by A1;
end;
