
theorem Th1046:
Sum digits(1679,10) = 23
proof
  thus Sum digits(1679,10) = Sum <%9,7,6%>+Sum <%1%> by Th1045,AFINSQ_2:55
  .= Sum <%9,7%> + Sum <%6%> + Sum <%1%> by AFINSQ_2:55
  .= (9 + 7) + Sum <%6%> + Sum <%1%> by AFINSQ_2:54
  .= (9 + 7 + 6) + Sum <%1%> by AFINSQ_2:53
  .= 22 + 1 by AFINSQ_2:53
  .= 23;
end;
