
theorem Th773:
Sum digits(594,10) = 18
proof
  thus Sum digits(594,10) = Sum <%4,9%>+Sum <%5%> by Th772,AFINSQ_2:55
  .= (4 + 9) + Sum <%5%> by AFINSQ_2:54
  .= 13 + 5 by AFINSQ_2:53
  .= 18;
end;
