reserve i,j,e,u for object;
reserve I for set; 
reserve x,X,Y,Z,V for ManySortedSet of I;

theorem Th95:
  Y (\) X = X (\+\) (X (\/) Y)
proof
A1: X c= Y (\/) X by Th14;
  thus Y (\) X = ((Y (\/) X) (\) X) by Th75
    .= EmptyMS I (\/) ((Y (\/) X) (\) X) by Th22,Th43
    .= X (\+\) (X (\/) Y) by A1,Th52;
end;
