
theorem Th730:
Sum digits(21,10) = 3
proof
  thus Sum digits(21,10) = Sum <%1%>+Sum <%2%> by Th729,AFINSQ_2:55
  .= 1 + Sum <%2%> by AFINSQ_2:53
  .= 1+2 by AFINSQ_2:53
  .= 3;
end;
