
theorem Th467:
Sum digits(1380,10) = 12
proof
  thus Sum digits(1380,10) = Sum <%0,8,3%>+Sum <%1%> by Th466,AFINSQ_2:55
  .= Sum <%0,8%> + Sum <%3%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 8) + Sum <%3%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 8 + 3) + Sum <%1%> by AFINSQ_2:53
  .= 11 + 1 by AFINSQ_2:53
  .= 12;
end;
