
theorem Th439:
Sum digits(1100,10) = 2
proof
  thus Sum digits(1100,10) = Sum <%0,0,1%>+Sum <%1%> by Th438,AFINSQ_2:55
  .= Sum <%0,0%> + Sum <%1%> + Sum <%1%> by AFINSQ_2:55
  .= (0 + 0) + Sum <%1%> + Sum <%1%> by AFINSQ_2:54
  .= (0 + 0 + 1) + Sum <%1%> by AFINSQ_2:53
  .= 1 + 1 by AFINSQ_2:53
  .= 2;
end;
