theorem
  sqrcomplex is_distributive_wrt multcomplex
proof
  let x1,x2 be Element of COMPLEX;
  thus sqrcomplex.(multcomplex.(x1,x2)) = sqrcomplex.(x1*x2) by BINOP_2:def 5
     .= (x1*x2)^2 by Def1
     .= x1^2*x2^2
     .= multcomplex.(x1^2,x2^2) by BINOP_2:def 5
     .= multcomplex.(sqrcomplex.x1,x2^2) by Def1
     .= multcomplex.(sqrcomplex.x1,sqrcomplex.x2) by Def1;
end;
