
theorem Th203:
Sum digits(320,10) = 5
proof
  thus Sum digits(320,10) = Sum <%0,2%>+Sum <%3%> by Th202,AFINSQ_2:55
  .= (0 + 2) + Sum <%3%> by AFINSQ_2:54
  .= 2 + 3 by AFINSQ_2:53
  .= 5;
end;
