
theorem Th835:
Sum digits(1386,10) = 18
proof
  thus Sum digits(1386,10) = Sum <%6,8,3%>+Sum <%1%> by Th834,AFINSQ_2:55
  .= Sum <%6,8%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (6 + 8) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (6 + 8 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 17 + 1 by AFINSQ_2:53
  .= 18;
end;
