
theorem Th459:
Sum digits(1300,10) = 4
proof
  thus Sum digits(1300,10) = Sum <%0,0,3%>+Sum <%1%> by Th458,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 0 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 3 + 1 by AFINSQ_2:53
  .= 4;
end;
