
theorem Th118:
Sum digits(117,10) = 9
proof
  thus Sum digits(117,10) = Sum <%7,1%>+Sum <%1%> by Th117,AFINSQ_2:55
  .= (7 + 1) + Sum <%1%> by AFINSQ_2:54
  .= 8 + 1 by AFINSQ_2:53
  .= 9;
end;
