
theorem Th744:
Sum digits(315,10) = 9
proof
  thus Sum digits(315,10) = Sum <%5,1%>+Sum <%3%> by Th743,AFINSQ_2:55
  .= (5 + 1) + Sum <%3%> by AFINSQ_2:54
  .= 6 + 3 by AFINSQ_2:53
  .= 9;
end;
