
theorem Th356:
Sum digits(855,10) = 18
proof
  thus Sum digits(855,10) = Sum <%5,5%>+Sum <%8%> by Th355,AFINSQ_2:55
  .= (5 + 5) + Sum <%8%> by AFINSQ_2:54
  .= 10 + 8 by AFINSQ_2:53
  .= 18;
end;
