
theorem Th505:
Sum digits(1760,10) = 14
proof
  thus Sum digits(1760,10) = Sum <%0,6,7%>+Sum <%1%> by Th504,AFINSQ_2:55
  .= Sum <%0,6%> + Sum <%7%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 6) + Sum <%7%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 6 + 7) + Sum <%1%> by AFINSQ_2:53
  .= 13 + 1 by AFINSQ_2:53
  .= 14;
end;
