
theorem Th1140:
Sum digits(1350,10) = 9
proof
  thus Sum digits(1350,10) = Sum <%0,5,3%>+Sum <%1%> by Th1139,AFINSQ_2:55
  .= Sum <%0,5%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 5) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 5 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 8 + 1 by AFINSQ_2:53
  .= 9;
end;
