
theorem Th1030:
Sum digits(1472,10) = 14
proof
  thus Sum digits(1472,10) = Sum <%2,7,4%>+Sum <%1%> by Th1029,AFINSQ_2:55
  .= Sum <%2,7%> + Sum <%4%> + Sum <%1%> by AFINSQ_2:55
  .= (2 + 7) + Sum <%4%> + Sum <%1%> by AFINSQ_2:54
  .= (2 + 7 + 4) + Sum <%1%> by AFINSQ_2:53
  .= 13 + 1 by AFINSQ_2:53
  .= 14;
end;
