
theorem Th613:
Sum digits(2840,10) = 14
proof
  thus Sum digits(2840,10) = Sum <%0,4,8%>+Sum <%2%> by Th612,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%8%> + Sum <%2%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%8%> + Sum <%2%> by AFINSQ_2:54
  .= (0 + 4 + 8) + Sum <%2%> by AFINSQ_2:53
  .= 12 + 2 by AFINSQ_2:53
  .= 14;
end;
