
theorem Th461:
Sum digits(1320,10) = 6
proof
  thus Sum digits(1320,10) = Sum <%0,2,3%>+Sum <%1%> by Th460,AFINSQ_2:55
  .= Sum <%0,2%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 2) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 2 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 5 + 1 by AFINSQ_2:53
  .= 6;
end;
