
theorem Th807:
Sum digits(1034,10) = 8
proof
  thus Sum digits(1034,10) = Sum <%4,3,0%>+Sum <%1%> by Th806,AFINSQ_2:55
  .= Sum <%4,3%> + Sum <%0%> + Sum <%1%> by AFINSQ_2:55
  .= (4 + 3) + Sum <%0%> + Sum <%1%> by AFINSQ_2:54
  .= (4 + 3 + 0) + Sum <%1%> by AFINSQ_2:53
  .= 7 + 1 by AFINSQ_2:53
  .= 8;
end;
