
theorem Th151:
Sum digits(126,10) = 9
proof
  thus Sum digits(126,10) = Sum <%6,2%>+Sum <%1%> by Th150,AFINSQ_2:55
  .= (6 + 2) + Sum <%1%> by AFINSQ_2:54
  .= 8 + 1 by AFINSQ_2:53
  .= 9;
end;
