
theorem Th833:
Sum digits(1364,10) = 14
proof
  thus Sum digits(1364,10) = Sum <%4,6,3%>+Sum <%1%> by Th832,AFINSQ_2:55
  .= Sum <%4,6%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (4 + 6) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (4 + 6 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 13 + 1 by AFINSQ_2:53
  .= 14;
end;
