
theorem Th1270:
Sum digits(3550,10) = 13
proof
  thus Sum digits(3550,10) = Sum <%0,5,5%>+Sum <%3%> by Th1269,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%5%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%5%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 5 + 5) + Sum <%3%> by AFINSQ_2:53
  .= 10 + 3 by AFINSQ_2:53
  .= 13;
end;
