
theorem Th312:
Sum digits(437,10) = 14
proof
  thus Sum digits(437,10) = Sum <%7,3%>+Sum <%4%> by Th311,AFINSQ_2:55
  .= (7 + 3) + Sum <%4%> by AFINSQ_2:54
  .= 10 + 4 by AFINSQ_2:53
  .= 14;
end;
