
theorem Th1024:
Sum digits(1403,10) = 8
proof
  thus Sum digits(1403,10) = Sum <%3,0,4%>+Sum <%1%> by Th1023,AFINSQ_2:55
  .= Sum <%3,0%> + Sum <%4%> + Sum <%1%> by AFINSQ_2:55
  .= (3 + 0) + Sum <%4%> + Sum <%1%> by AFINSQ_2:54
  .= (3 + 0 + 4) + Sum <%1%> by AFINSQ_2:53
  .= 7 + 1 by AFINSQ_2:53
  .= 8;
end;
