
theorem Th857:
Sum digits(1650,10) = 12
proof
  thus Sum digits(1650,10) = Sum <%0,5,6%>+Sum <%1%> by Th856,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%6%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%6%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 5 + 6) + Sum <%1%> by AFINSQ_2:53
  .= 11 + 1 by AFINSQ_2:53
  .= 12;
end;
