
theorem Th643:
Sum digits(3140,10) = 8
proof
  thus Sum digits(3140,10) = Sum <%0,4,1%>+Sum <%3%> by Th642,AFINSQ_2:55
  .= Sum <%0,4%> + Sum <%1%> + Sum <%3%> by AFINSQ_2:55
  .= (0 + 4) + Sum <%1%> + Sum <%3%> by AFINSQ_2:54
  .= (0 + 4 + 1) + Sum <%3%> by AFINSQ_2:53
  .= 5 + 3 by AFINSQ_2:53
  .= 8;
end;
