
theorem Th1114:
Sum digits(875,10) = 20
proof
  thus Sum digits(875,10) = Sum <%5,7%>+Sum <%8%> by Th1113,AFINSQ_2:55
  .= (5 + 7) + Sum <%8%> by AFINSQ_2:54
  .= 12 + 8 by AFINSQ_2:53
  .= 20;
end;
