 reserve x,y,X,Y for set;
reserve G for non empty multMagma,
  D for set,
  a,b,c,r,l for Element of G;

theorem Th4:
  G is unital implies
    the_unity_wrt the multF of G is_a_unity_wrt the multF of G
proof
  given a such that
A1: a is_a_unity_wrt op(G);
  thus thesis by A1,BINOP_1:def 8;
end;
