
theorem Th1042:
Sum digits(1633,10) = 13
proof
  thus Sum digits(1633,10) = Sum <%3,3,6%>+Sum <%1%> by Th1041,AFINSQ_2:55
  .= Sum <%3,3%> + Sum <%6%> + Sum <%1%> by AFINSQ_2:55
  .= (3 + 3) + Sum <%6%> + Sum <%1%> by AFINSQ_2:54
  .= (3 + 3 + 6) + Sum <%1%> by AFINSQ_2:53
  .= 12 + 1 by AFINSQ_2:53
  .= 13;
end;
