reserve x, y for object, X, X1, X2 for set;
reserve Y, Y1, Y2 for complex-functions-membered set,
  c, c1, c2 for Complex,
  f for PartFunc of X,Y,
  f1 for PartFunc of X1,Y1,
  f2 for PartFunc of X2, Y2,
  g, h, k for complex-valued Function;

theorem Th27:
  - (g /" h) = g /" -h
proof
A1: dom -h = dom h by VALUED_1:8;
  dom(g/"h) = dom g /\ dom h & dom(g/"-h) = dom g /\ dom -h by VALUED_1:16;
  hence dom -(g/"h) = dom(g/"-h) by A1,VALUED_1:8;
  let x be object;
  assume x in dom -(g/"h);
  thus (-(g/"h)).x = -(g/"h).x by VALUED_1:8
    .= -(g.x/h.x) by VALUED_1:17
    .= g.x/-h.x by XCMPLX_1:188
    .= g.x/(-h).x by VALUED_1:8
    .= (g/"-h).x by VALUED_1:17;
end;
